Get this exception after upgrading through the management page. Workaround is to revert back to the 1.312 hudson.war.

Status Code: 500
Exception:
Stacktrace:

org.apache.commons.jelly.JellyTagException: jar:file:/home/jjohnson/hudson/war/WEB-INF/lib/hudson-core-1.342.jar!/lib/layout/layout.jelly:123:53: hudson/maven/MavenReporter
at org.apache.commons.jelly.impl.TagScript.handleException(TagScript.java:714)
at org.apache.commons.jelly.impl.TagScript.run(TagScript.java:283)
at org.apache.commons.jelly.impl.ScriptBlock.run(ScriptBlock.java:95)
at org.apache.commons.jelly.TagSupport.invokeBody(TagSupport.java:186)
at org.apache.commons.jelly.impl.StaticTag.doTag(StaticTag.java:65)
at org.apache.commons.jelly.impl.StaticTagScript.run(StaticTagScript.java:112)
at org.apache.commons.jelly.impl.ScriptBlock.run(ScriptBlock.java:95)
at org.apache.commons.jelly.TagSupport.invokeBody(TagSupport.java:186)
at org.apache.commons.jelly.impl.StaticTag.doTag(StaticTag.java:65)
at org.apache.commons.jelly.impl.StaticTagScript.run(StaticTagScript.java:112)
at org.apache.commons.jelly.impl.ScriptBlock.run(ScriptBlock.java:95)
at org.apache.commons.jelly.TagSupport.invokeBody(TagSupport.java:186)
at org.apache.commons.jelly.tags.core.JellyTag.doTag(JellyTag.java:45)
at org.apache.commons.jelly.impl.TagScript.run(TagScript.java:263)
at org.apache.commons.jelly.impl.DynamicTag.doTag(DynamicTag.java:81)
at org.apache.commons.jelly.impl.TagScript.run(TagScript.java:263)
at org.apache.commons.jelly.impl.ScriptBlock.run(ScriptBlock.java:95)
at org.apache.commons.jelly.TagSupport.invokeBody(TagSupport.java:186)
at org.apache.commons.jelly.tags.core.JellyTag.doTag(JellyTag.java:45)
at org.apache.commons.jelly.impl.TagScript.run(TagScript.java:263)
at org.kohsuke.stapler.jelly.DefaultScriptInvoker.invokeScript(DefaultScriptInvoker.java:37)
at org.kohsuke.stapler.jelly.DefaultScriptInvoker.invokeScript(DefaultScriptInvoker.java:27)
at org.kohsuke.stapler.jelly.JellyClassTearOff.serveIndexJelly(JellyClassTearOff.java:43)
at org.kohsuke.stapler.jelly.JellyFacet.handleIndexRequest(JellyFacet.java:83)
at org.kohsuke.stapler.Stapler.invoke(Stapler.java:508)
at org.kohsuke.stapler.Stapler.invoke(Stapler.java:435)
at org.kohsuke.stapler.Stapler.service(Stapler.java:123)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:45)
at winstone.ServletConfiguration.execute(ServletConfiguration.java:249)
at winstone.RequestDispatcher.forward(RequestDispatcher.java:335)
at winstone.RequestDispatcher.doFilter(RequestDispatcher.java:378)
at hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:94)
at hudson.util.PluginServletFilter.doFilter(PluginServletFilter.java:86)
at winstone.FilterConfiguration.execute(FilterConfiguration.java:195)
at winstone.RequestDispatcher.doFilter(RequestDispatcher.java:368)
at hudson.security.csrf.CrumbFilter.doFilter(CrumbFilter.java:47)
at winstone.FilterConfiguration.execute(FilterConfiguration.java:195)
at winstone.RequestDispatcher.doFilter(RequestDispatcher.java:368)
at hudson.security.HudsonFilter.doFilter(HudsonFilter.java:162)
at winstone.FilterConfiguration.execute(FilterConfiguration.java:195)
at winstone.RequestDispatcher.doFilter(RequestDispatcher.java:368)
at winstone.RequestDispatcher.forward(RequestDispatcher.java:333)
at winstone.RequestHandlerThread.processRequest(RequestHandlerThread.java:244)
at winstone.RequestHandlerThread.run(RequestHandlerThread.java:150)
at java.lang.Thread.run(Thread.java:619)
Caused by: java.lang.NoClassDefFoundError: hudson/maven/MavenReporter
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:621)
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:124)
at java.net.URLClassLoader.defineClass(URLClassLoader.java:260)
at java.net.URLClassLoader.access$000(URLClassLoader.java:56)
at java.net.URLClassLoader$1.run(URLClassLoader.java:195)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:188)
at java.lang.ClassLoader.loadClass(ClassLoader.java:307)
at java.lang.ClassLoader.loadClass(ClassLoader.java:252)
at hudson.PluginManager$UberClassLoader.findClass(PluginManager.java:555)
at java.lang.ClassLoader.loadClass(ClassLoader.java:307)
at java.lang.ClassLoader.loadClass(ClassLoader.java:252)
at net.java.sezpoz.IndexItem.element(IndexItem.java:114)
at hudson.ExtensionFinder$Sezpoz.findExtensions(ExtensionFinder.java:87)
at hudson.ExtensionList.load(ExtensionList.java:198)
at hudson.ExtensionList.ensureLoaded(ExtensionList.java:181)
at hudson.ExtensionList.iterator(ExtensionList.java:112)
at hudson.ExtensionList.load(ExtensionList.java:197)
at hudson.ExtensionList.ensureLoaded(ExtensionList.java:181)
at hudson.ExtensionList.iterator(ExtensionList.java:112)
at org.apache.commons.jelly.expression.ExpressionSupport.evaluateAsIterator(ExpressionSupport.java:101)
at org.apache.commons.jelly.tags.core.ForEachTag.doTag(ForEachTag.java:89)
at org.apache.commons.jelly.impl.TagScript.run(TagScript.java:263)
... 43 more
Caused by: java.lang.ClassNotFoundException: hudson.maven.MavenReporter
at java.net.URLClassLoader$1.run(URLClassLoader.java:200)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:188)
at java.lang.ClassLoader.loadClass(ClassLoader.java:307)
at java.lang.ClassLoader.loadClass(ClassLoader.java:252)
at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:320)
... 67 more

Generated by Winstone Servlet Engine v0.9.10 at Tue Jan 26 10:50:29 EST 2010