At startup, I see this exception in the log of tomcat :

04-Dec-2012 09:29:58 hudson.ExtensionFinder$Sezpoz scout
WARNING: Failed to scout org.jenkinsci.plugins.configfiles.maven.job.MvnGlobalSettingsProvider$DescriptorImpl
java.lang.InstantiationException: file:/d:/data/Jenkins/plugins/config-file-provider/WEB-INF/classes/META-INF/annotations/hudson.Extension might need to be rebuilt: java.lang.ClassNotFoundException: org.jenkinsci.plugins.configfiles.maven.job.MvnGlobalSettingsProvider$DescriptorImpl
at net.java.sezpoz.IndexItem.element(IndexItem.java:144)
at hudson.ExtensionFinder$Sezpoz.scout(ExtensionFinder.java:649)
at hudson.ClassicPluginStrategy.findComponents(ClassicPluginStrategy.java:290)
at hudson.ExtensionList.load(ExtensionList.java:295)
at hudson.ExtensionList.ensureLoaded(ExtensionList.java:248)
at hudson.ExtensionList.iterator(ExtensionList.java:138)
at hudson.ClassicPluginStrategy.findComponents(ClassicPluginStrategy.java:289)
at hudson.ExtensionList.load(ExtensionList.java:295)
at hudson.ExtensionList.ensureLoaded(ExtensionList.java:248)
at hudson.ExtensionList.iterator(ExtensionList.java:138)
at jenkins.model.Jenkins.getDescriptorByType(Jenkins.java:1148)
at hudson.plugins.copyartifact.BuildSelectorParameter.initAliases(BuildSelectorParameter.java:100)
at hudson.plugins.copyartifact.CopyArtifactPlugin.postInitialize(CopyArtifactPlugin.java:35)
at hudson.PluginManager$2$1$2.run(PluginManager.java:352)
at org.jvnet.hudson.reactor.TaskGraphBuilder$TaskImpl.run(TaskGraphBuilder.java:146)
at org.jvnet.hudson.reactor.Reactor.runTask(Reactor.java:259)
at jenkins.model.Jenkins$7.runTask(Jenkins.java:883)
at org.jvnet.hudson.reactor.Reactor$2.run(Reactor.java:187)
at org.jvnet.hudson.reactor.Reactor$Node.run(Reactor.java:94)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
at java.lang.Thread.run(Thread.java:662)
Caused by: java.lang.ClassNotFoundException: org.jenkinsci.plugins.configfiles.maven.job.MvnGlobalSettingsProvider$DescriptorImpl
at hudson.PluginManager$UberClassLoader.findClass(PluginManager.java:935)
at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
at net.java.sezpoz.IndexItem.element(IndexItem.java:134)
... 21 more