To reproduce you just have to install Jenkins v1.472 from scratch and add DropDown ViewsTabBar Plugin to Jenkins. Once you choose "DropDownViewsTabVar provides a drop down menu for selecting views." and save this setting, any further changes in "Configure System", which tried to be saved, will cause an exception being thrown.

Can you please check this? Thanks!

Status Code: 500
Exception: java.lang.IllegalArgumentException: Failed to instantiate class hudson.views.ViewsTabBar from

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

Stacktrace:

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"]}

at org.kohsuke.stapler.Stapler.tryInvoke(Stapler.java:616)
at org.kohsuke.stapler.Stapler.invoke(Stapler.java:659)
at org.kohsuke.stapler.Stapler.invoke(Stapler.java:488)
at org.kohsuke.stapler.Stapler.service(Stapler.java:162)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:45)
at winstone.ServletConfiguration.execute(ServletConfiguration.java:248)
at winstone.RequestDispatcher.forward(RequestDispatcher.java:333)
at winstone.RequestDispatcher.doFilter(RequestDispatcher.java:376)
at hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:95)
at net.bull.javamelody.MonitoringFilter.doFilter(MonitoringFilter.java:202)
at net.bull.javamelody.MonitoringFilter.doFilter(MonitoringFilter.java:175)
at net.bull.javamelody.PluginMonitoringFilter.doFilter(PluginMonitoringFilter.java:86)
at org.jvnet.hudson.plugins.monitoring.HudsonMonitoringFilter.doFilter(HudsonMonitoringFilter.java:84)
at hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:98)
at hudson.plugins.greenballs.GreenBallFilter.doFilter(GreenBallFilter.java:58)
at hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:98)
at hudson.plugins.audit_trail.AuditTrailFilter.doFilter(AuditTrailFilter.java:66)
at hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:98)
at hudson.util.PluginServletFilter.doFilter(PluginServletFilter.java:87)
at winstone.FilterConfiguration.execute(FilterConfiguration.java:194)
at winstone.RequestDispatcher.doFilter(RequestDispatcher.java:366)
at hudson.security.csrf.CrumbFilter.doFilter(CrumbFilter.java:47)
at winstone.FilterConfiguration.execute(FilterConfiguration.java:194)
at winstone.RequestDispatcher.doFilter(RequestDispatcher.java:366)
at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:84)
at hudson.security.UnwrapSecurityExceptionFilter.doFilter(UnwrapSecurityExceptionFilter.java:51)
at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
at org.acegisecurity.ui.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:166)
at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
at org.acegisecurity.providers.anonymous.AnonymousProcessingFilter.doFilter(AnonymousProcessingFilter.java:125)
at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
at org.acegisecurity.ui.rememberme.RememberMeProcessingFilter.doFilter(RememberMeProcessingFilter.java:142)
at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
at org.acegisecurity.ui.AbstractProcessingFilter.doFilter(AbstractProcessingFilter.java:271)
at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
at org.acegisecurity.ui.basicauth.BasicProcessingFilter.doFilter(BasicProcessingFilter.java:173)
at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
at jenkins.security.ApiTokenFilter.doFilter(ApiTokenFilter.java:63)
at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
at org.acegisecurity.context.HttpSessionContextIntegrationFilter.doFilter(HttpSessionContextIntegrationFilter.java:249)
at hudson.security.HttpSessionContextIntegrationFilter2.doFilter(HttpSessionContextIntegrationFilter2.java:66)
at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:87)
at hudson.security.ChainedServletFilter.doFilter(ChainedServletFilter.java:76)
at hudson.security.HudsonFilter.doFilter(HudsonFilter.java:164)
at winstone.FilterConfiguration.execute(FilterConfiguration.java:194)
at winstone.RequestDispatcher.doFilter(RequestDispatcher.java:366)
at org.kohsuke.stapler.compression.CompressionFilter.doFilter(CompressionFilter.java:50)
at winstone.FilterConfiguration.execute(FilterConfiguration.java:194)
at winstone.RequestDispatcher.doFilter(RequestDispatcher.java:366)
at hudson.util.CharacterEncodingFilter.doFilter(CharacterEncodingFilter.java:81)
at winstone.FilterConfiguration.execute(FilterConfiguration.java:194)
at winstone.RequestDispatcher.doFilter(RequestDispatcher.java:366)
at winstone.RequestDispatcher.forward(RequestDispatcher.java:331)
at winstone.RequestHandlerThread.processRequest(RequestHandlerThread.java:215)
at winstone.RequestHandlerThread.run(RequestHandlerThread.java:138)
at java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source)
at java.util.concurrent.FutureTask$Sync.innerRun(Unknown Source)
at java.util.concurrent.FutureTask.run(Unknown Source)
at winstone.BoundedExecutorService$1.run(BoundedExecutorService.java:77)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
Caused by: java.lang.IllegalArgumentException: Failed to instantiate class hudson.views.ViewsTabBar from

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

at org.kohsuke.stapler.RequestImpl$TypePair.convertJSON(RequestImpl.java:633)
at org.kohsuke.stapler.RequestImpl.bindJSON(RequestImpl.java:377)
at org.kohsuke.stapler.RequestImpl.bindJSON(RequestImpl.java:373)
at hudson.views.ViewsTabBar$GlobalConfigurationImpl.configure(ViewsTabBar.java:84)
at jenkins.model.Jenkins.configureDescriptor(Jenkins.java:2686)
at jenkins.model.Jenkins.doConfigSubmit(Jenkins.java:2649)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.kohsuke.stapler.Function$InstanceFunction.invoke(Function.java:288)
at org.kohsuke.stapler.Function.bindAndInvoke(Function.java:151)
at org.kohsuke.stapler.Function.bindAndInvokeAndServeResponse(Function.java:90)
at org.kohsuke.stapler.MetaClass$1.doDispatch(MetaClass.java:111)
at org.kohsuke.stapler.NameBasedDispatcher.dispatch(NameBasedDispatcher.java:53)
at org.kohsuke.stapler.Stapler.tryInvoke(Stapler.java:574)
... 61 more
Caused by: java.lang.IllegalArgumentException: Class ["hudson.views.DefaultViewsTabBar","hudson.views.tabbar.DropDownViewsTabBar"] is specified in JSON, but no such class found in classLoader hudson.PluginManager$UberClassLoader
at org.kohsuke.stapler.RequestImpl$TypePair.convertJSON(RequestImpl.java:606)
... 76 more
Caused by: java.lang.ClassNotFoundException: ["hudson.views.DefaultViewsTabBar","hudson.views.tabbar.DropDownViewsTabBar"]
at hudson.PluginManager$UberClassLoader.findClass(PluginManager.java:782)
at java.lang.ClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at org.kohsuke.stapler.RequestImpl$TypePair.convertJSON(RequestImpl.java:601)
... 76 more