I have the dropdown views tabbar enabled, and am usign Jenkins 1.455 When I go to save the main Jenkins config page, I see this CNF exception in the browser:

exception

javax.servlet.ServletException: java.lang.IllegalArgumentException: Failed to instantiate class hudson.views.ViewsTabBar from

{"showJobCount":false,"stapler-class":["hudson.views.DefaultViewsTabBar","hudson.views.tabbar.DropDownViewsTabBar"]}

org.kohsuke.stapler.Stapler.tryInvoke(Stapler.java:605)
org.kohsuke.stapler.Stapler.invoke(Stapler.java:648)
org.kohsuke.stapler.Stapler.invoke(Stapler.java:477)
org.kohsuke.stapler.Stapler.service(Stapler.java:159)
javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:95)
net.bull.javamelody.MonitoringFilter.doFilter(MonitoringFilter.java:185)
net.bull.javamelody.MonitoringFilter.doFilter(MonitoringFilter.java:159)
net.bull.javamelody.PluginMonitoringFilter.doFilter(PluginMonitoringFilter.java:86)
org.jvnet.hudson.plugins.monitoring.HudsonMonitoringFilter.doFilter(HudsonMonitoringFilter.java:84)
hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:98)
hudson.plugins.audit_trail.AuditTrailFilter.doFilter(AuditTrailFilter.java:66)
hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:98)
oracle.boulderlabs.jenkins.validatorkiller.ValidatorKiller.doFilter(ValidatorKiller.java:63)
hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:98)
hudson.util.PluginServletFilter.doFilter(PluginServletFilter.java:87)
hudson.security.csrf.CrumbFilter.doFilter(CrumbFilter.java:47)
hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:84)
hudson.security.UnwrapSecurityExceptionFilter.doFilter(UnwrapSecurityExceptionFilter.java:51)
hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
org.acegisecurity.ui.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:166)
hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
org.acegisecurity.providers.anonymous.AnonymousProcessingFilter.doFilter(AnonymousProcessingFilter.java:125)
hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
org.acegisecurity.ui.rememberme.RememberMeProcessingFilter.doFilter(RememberMeProcessingFilter.java:142)
hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
org.acegisecurity.ui.AbstractProcessingFilter.doFilter(AbstractProcessingFilter.java:271)
hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
org.acegisecurity.ui.basicauth.BasicProcessingFilter.doFilter(BasicProcessingFilter.java:173)
hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
jenkins.security.ApiTokenFilter.doFilter(ApiTokenFilter.java:61)
hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
org.acegisecurity.context.HttpSessionContextIntegrationFilter.doFilter(HttpSessionContextIntegrationFilter.java:249)
hudson.security.HttpSessionContextIntegrationFilter2.doFilter(HttpSessionContextIntegrationFilter2.java:66)
hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
hudson.security.ChainedServletFilter.doFilter(ChainedServletFilter.java:76)
hudson.security.HudsonFilter.doFilter(HudsonFilter.java:164)
hudson.util.CharacterEncodingFilter.doFilter(CharacterEncodingFilter.java:81)

root cause

java.lang.IllegalArgumentException: Failed to instantiate class hudson.views.ViewsTabBar from

{"showJobCount":false,"stapler-class":["hudson.views.DefaultViewsTabBar","hudson.views.tabbar.DropDownViewsTabBar"]}

org.kohsuke.stapler.RequestImpl$TypePair.convertJSON(RequestImpl.java:633)
org.kohsuke.stapler.RequestImpl.bindJSON(RequestImpl.java:377)
org.kohsuke.stapler.RequestImpl.bindJSON(RequestImpl.java:373)
hudson.views.ViewsTabBar$GlobalConfigurationImpl.configure(ViewsTabBar.java:84)
jenkins.model.Jenkins.configureDescriptor(Jenkins.java:2620)
jenkins.model.Jenkins.doConfigSubmit(Jenkins.java:2583)
sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
java.lang.reflect.Method.invoke(Method.java:597)
org.kohsuke.stapler.Function$InstanceFunction.invoke(Function.java:288)
org.kohsuke.stapler.Function.bindAndInvoke(Function.java:151)
org.kohsuke.stapler.Function.bindAndInvokeAndServeResponse(Function.java:90)
org.kohsuke.stapler.MetaClass$1.doDispatch(MetaClass.java:111)
org.kohsuke.stapler.NameBasedDispatcher.dispatch(NameBasedDispatcher.java:53)
org.kohsuke.stapler.Stapler.tryInvoke(Stapler.java:563)
org.kohsuke.stapler.Stapler.invoke(Stapler.java:648)
org.kohsuke.stapler.Stapler.invoke(Stapler.java:477)
org.kohsuke.stapler.Stapler.service(Stapler.java:159)
javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:95)
net.bull.javamelody.MonitoringFilter.doFilter(MonitoringFilter.java:185)
net.bull.javamelody.MonitoringFilter.doFilter(MonitoringFilter.java:159)
net.bull.javamelody.PluginMonitoringFilter.doFilter(PluginMonitoringFilter.java:86)
org.jvnet.hudson.plugins.monitoring.HudsonMonitoringFilter.doFilter(HudsonMonitoringFilter.java:84)
hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:98)
hudson.plugins.audit_trail.AuditTrailFilter.doFilter(AuditTrailFilter.java:66)
hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:98)
oracle.boulderlabs.jenkins.validatorkiller.ValidatorKiller.doFilter(ValidatorKiller.java:63)
hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:98)
hudson.util.PluginServletFilter.doFilter(PluginServletFilter.java:87)
hudson.security.csrf.CrumbFilter.doFilter(CrumbFilter.java:47)
hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:84)
hudson.security.UnwrapSecurityExceptionFilter.doFilter(UnwrapSecurityExceptionFilter.java:51)
hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
org.acegisecurity.ui.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:166)
hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
org.acegisecurity.providers.anonymous.AnonymousProcessingFilter.doFilter(AnonymousProcessingFilter.java:125)
hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
org.acegisecurity.ui.rememberme.RememberMeProcessingFilter.doFilter(RememberMeProcessingFilter.java:142)
hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
org.acegisecurity.ui.AbstractProcessingFilter.doFilter(AbstractProcessingFilter.java:271)
hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
org.acegisecurity.ui.basicauth.BasicProcessingFilter.doFilter(BasicProcessingFilter.java:173)
hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
jenkins.security.ApiTokenFilter.doFilter(ApiTokenFilter.java:61)
hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
org.acegisecurity.context.HttpSessionContextIntegrationFilter.doFilter(HttpSessionContextIntegrationFilter.java:249)
hudson.security.HttpSessionContextIntegrationFilter2.doFilter(HttpSessionContextIntegrationFilter2.java:66)
hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
hudson.security.ChainedServletFilter.doFilter(ChainedServletFilter.java:76)
hudson.security.HudsonFilter.doFilter(HudsonFilter.java:164)
hudson.util.CharacterEncodingFilter.doFilter(CharacterEncodingFilter.java:81)

root cause

java.lang.IllegalArgumentException: Class ["hudson.views.DefaultViewsTabBar","hudson.views.tabbar.DropDownViewsTabBar"] is specified in JSON, but no such class found in classLoader hudson.PluginManager$UberClassLoader
org.kohsuke.stapler.RequestImpl$TypePair.convertJSON(RequestImpl.java:606)
org.kohsuke.stapler.RequestImpl.bindJSON(RequestImpl.java:377)
org.kohsuke.stapler.RequestImpl.bindJSON(RequestImpl.java:373)
hudson.views.ViewsTabBar$GlobalConfigurationImpl.configure(ViewsTabBar.java:84)
jenkins.model.Jenkins.configureDescriptor(Jenkins.java:2620)
jenkins.model.Jenkins.doConfigSubmit(Jenkins.java:2583)
sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
java.lang.reflect.Method.invoke(Method.java:597)
org.kohsuke.stapler.Function$InstanceFunction.invoke(Function.java:288)
org.kohsuke.stapler.Function.bindAndInvoke(Function.java:151)
org.kohsuke.stapler.Function.bindAndInvokeAndServeResponse(Function.java:90)
org.kohsuke.stapler.MetaClass$1.doDispatch(MetaClass.java:111)
org.kohsuke.stapler.NameBasedDispatcher.dispatch(NameBasedDispatcher.java:53)
org.kohsuke.stapler.Stapler.tryInvoke(Stapler.java:563)
org.kohsuke.stapler.Stapler.invoke(Stapler.java:648)
org.kohsuke.stapler.Stapler.invoke(Stapler.java:477)
org.kohsuke.stapler.Stapler.service(Stapler.java:159)
javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:95)
net.bull.javamelody.MonitoringFilter.doFilter(MonitoringFilter.java:185)
net.bull.javamelody.MonitoringFilter.doFilter(MonitoringFilter.java:159)
net.bull.javamelody.PluginMonitoringFilter.doFilter(PluginMonitoringFilter.java:86)
org.jvnet.hudson.plugins.monitoring.HudsonMonitoringFilter.doFilter(HudsonMonitoringFilter.java:84)
hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:98)
hudson.plugins.audit_trail.AuditTrailFilter.doFilter(AuditTrailFilter.java:66)
hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:98)
oracle.boulderlabs.jenkins.validatorkiller.ValidatorKiller.doFilter(ValidatorKiller.java:63)
hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:98)
hudson.util.PluginServletFilter.doFilter(PluginServletFilter.java:87)
hudson.security.csrf.CrumbFilter.doFilter(CrumbFilter.java:47)
hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:84)
hudson.security.UnwrapSecurityExceptionFilter.doFilter(UnwrapSecurityExceptionFilter.java:51)
hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
org.acegisecurity.ui.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:166)
hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
org.acegisecurity.providers.anonymous.AnonymousProcessingFilter.doFilter(AnonymousProcessingFilter.java:125)
hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
org.acegisecurity.ui.rememberme.RememberMeProcessingFilter.doFilter(RememberMeProcessingFilter.java:142)
hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
org.acegisecurity.ui.AbstractProcessingFilter.doFilter(AbstractProcessingFilter.java:271)
hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
org.acegisecurity.ui.basicauth.BasicProcessingFilter.doFilter(BasicProcessingFilter.java:173)
hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
jenkins.security.ApiTokenFilter.doFilter(ApiTokenFilter.java:61)
hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
org.acegisecurity.context.HttpSessionContextIntegrationFilter.doFilter(HttpSessionContextIntegrationFilter.java:249)
hudson.security.HttpSessionContextIntegrationFilter2.doFilter(HttpSessionContextIntegrationFilter2.java:66)
hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
hudson.security.ChainedServletFilter.doFilter(ChainedServletFilter.java:76)
hudson.security.HudsonFilter.doFilter(HudsonFilter.java:164)
hudson.util.CharacterEncodingFilter.doFilter(CharacterEncodingFilter.java:81)

root cause

java.lang.ClassNotFoundException: ["hudson.views.DefaultViewsTabBar","hudson.views.tabbar.DropDownViewsTabBar"]
hudson.PluginManager$UberClassLoader.findClass(PluginManager.java:747)
java.lang.ClassLoader.loadClass(ClassLoader.java:306)
java.lang.ClassLoader.loadClass(ClassLoader.java:247)
org.kohsuke.stapler.RequestImpl$TypePair.convertJSON(RequestImpl.java:601)
org.kohsuke.stapler.RequestImpl.bindJSON(RequestImpl.java:377)
org.kohsuke.stapler.RequestImpl.bindJSON(RequestImpl.java:373)
hudson.views.ViewsTabBar$GlobalConfigurationImpl.configure(ViewsTabBar.java:84)
jenkins.model.Jenkins.configureDescriptor(Jenkins.java:2620)
jenkins.model.Jenkins.doConfigSubmit(Jenkins.java:2583)
sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
java.lang.reflect.Method.invoke(Method.java:597)
org.kohsuke.stapler.Function$InstanceFunction.invoke(Function.java:288)
org.kohsuke.stapler.Function.bindAndInvoke(Function.java:151)
org.kohsuke.stapler.Function.bindAndInvokeAndServeResponse(Function.java:90)
org.kohsuke.stapler.MetaClass$1.doDispatch(MetaClass.java:111)
org.kohsuke.stapler.NameBasedDispatcher.dispatch(NameBasedDispatcher.java:53)
org.kohsuke.stapler.Stapler.tryInvoke(Stapler.java:563)
org.kohsuke.stapler.Stapler.invoke(Stapler.java:648)
org.kohsuke.stapler.Stapler.invoke(Stapler.java:477)
org.kohsuke.stapler.Stapler.service(Stapler.java:159)
javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:95)
net.bull.javamelody.MonitoringFilter.doFilter(MonitoringFilter.java:185)
net.bull.javamelody.MonitoringFilter.doFilter(MonitoringFilter.java:159)
net.bull.javamelody.PluginMonitoringFilter.doFilter(PluginMonitoringFilter.java:86)
org.jvnet.hudson.plugins.monitoring.HudsonMonitoringFilter.doFilter(HudsonMonitoringFilter.java:84)
hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:98)
hudson.plugins.audit_trail.AuditTrailFilter.doFilter(AuditTrailFilter.java:66)
hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:98)
oracle.boulderlabs.jenkins.validatorkiller.ValidatorKiller.doFilter(ValidatorKiller.java:63)
hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:98)
hudson.util.PluginServletFilter.doFilter(PluginServletFilter.java:87)
hudson.security.csrf.CrumbFilter.doFilter(CrumbFilter.java:47)
hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:84)
hudson.security.UnwrapSecurityExceptionFilter.doFilter(UnwrapSecurityExceptionFilter.java:51)
hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
org.acegisecurity.ui.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:166)
hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
org.acegisecurity.providers.anonymous.AnonymousProcessingFilter.doFilter(AnonymousProcessingFilter.java:125)
hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
org.acegisecurity.ui.rememberme.RememberMeProcessingFilter.doFilter(RememberMeProcessingFilter.java:142)
hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
org.acegisecurity.ui.AbstractProcessingFilter.doFilter(AbstractProcessingFilter.java:271)
hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
org.acegisecurity.ui.basicauth.BasicProcessingFilter.doFilter(BasicProcessingFilter.java:173)
hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
jenkins.security.ApiTokenFilter.doFilter(ApiTokenFilter.java:61)
hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
org.acegisecurity.context.HttpSessionContextIntegrationFilter.doFilter(HttpSessionContextIntegrationFilter.java:249)
hudson.security.HttpSessionContextIntegrationFilter2.doFilter(HttpSessionContextIntegrationFilter2.java:66)
hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
hudson.security.ChainedServletFilter.doFilter(ChainedServletFilter.java:76)
hudson.security.HudsonFilter.doFilter(HudsonFilter.java:164)
hudson.util.CharacterEncodingFilter.doFilter(CharacterEncodingFilter.java:81)