I installed the latest versions of the checkstyle and Findbugs plugins, and after a server restart I visited the plugin page and those two were NOT listed in the list of installed plugins. Also, there are no checkboxes to turn on findbugs or checkstyle for any of my jobs.

Stack traces from hudson log file:
SEVERE: Failed Loading plugin checkstyle
java.io.IOException: Dependency analysis-core (1.0) doesn't exist
at hudson.ClassicPluginStrategy.loadPluginDependencies(ClassicPluginStrategy.java:374)
at hudson.ClassicPluginStrategy.load(ClassicPluginStrategy.java:237)
at hudson.PluginManager$1$3$2$1.run(PluginManager.java:202)
at org.jvnet.hudson.reactor.TaskGraphBuilder$TaskImpl.run(TaskGraphBuilder.java:146)
at org.jvnet.hudson.reactor.Reactor.runTask(Reactor.java:259)
at hudson.model.Hudson$3.runTask(Hudson.java:642)
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:619)
Dec 8, 2009 12:47:51 PM hudson.model.Hudson$4 onTaskFailed
SEVERE: Failed Loading plugin findbugs
java.io.IOException: Dependency analysis-core (1.0) doesn't exist
at hudson.ClassicPluginStrategy.loadPluginDependencies(ClassicPluginStrategy.java:374)
at hudson.ClassicPluginStrategy.load(ClassicPluginStrategy.java:237)
at hudson.PluginManager$1$3$2$1.run(PluginManager.java:202)
at org.jvnet.hudson.reactor.TaskGraphBuilder$TaskImpl.run(TaskGraphBuilder.java:146)
at org.jvnet.hudson.reactor.Reactor.runTask(Reactor.java:259)
at hudson.model.Hudson$3.runTask(Hudson.java:642)
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:619)
Dec 8, 2009 12:47:51 PM hudson.model.Hudson$4 onAttained
INFO: Prepared all plugins
Dec 8, 2009 12:47:51 PM hudson.model.Hudson$4 onTaskFailed
SEVERE: Failed Initializing plugin checkstyle
java.lang.NullPointerException
at hudson.PluginManager$1$3$2$2.run(PluginManager.java:218)
at org.jvnet.hudson.reactor.TaskGraphBuilder$TaskImpl.run(TaskGraphBuilder.java:146)
at org.jvnet.hudson.reactor.Reactor.runTask(Reactor.java:259)
at hudson.model.Hudson$3.runTask(Hudson.java:642)
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:619)
Dec 8, 2009 12:47:51 PM hudson.model.Hudson$4 onTaskFailed
SEVERE: Failed Initializing plugin findbugs
java.lang.NullPointerException
at hudson.PluginManager$1$3$2$2.run(PluginManager.java:218)
at org.jvnet.hudson.reactor.TaskGraphBuilder$TaskImpl.run(TaskGraphBuilder.java:146)
at org.jvnet.hudson.reactor.Reactor.runTask(Reactor.java:259)
at hudson.model.Hudson$3.runTask(Hudson.java:642)
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:619)
Dec 8, 2009 12:47:51 PM hudson.model.Hudson$4 onAttained
INFO: Started all plugins
Dec 8, 2009 12:47:52 PM hudson.util.CopyOnWriteList$ConverterImpl unmarshal
WARNING: Failed to resolve class
com.thoughtworks.xstream.mapper.CannotResolveClassException: hudson.plugins.checkstyle.CheckStylePublisher : hudson.plugins.checkstyle.CheckStylePublisher
at com.thoughtworks.xstream.mapper.DefaultMapper.realClass(DefaultMapper.java:68)
at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:38)
at com.thoughtworks.xstream.mapper.XStream11XmlFriendlyMapper.realClass(XStream11XmlFriendlyMapper.java:34)
at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:38)
at com.thoughtworks.xstream.mapper.DynamicProxyMapper.realClass(DynamicProxyMapper.java:71)
at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:38)
at com.thoughtworks.xstream.mapper.PackageAliasingMapper.realClass(PackageAliasingMapper.java:88)
at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:38)
at com.thoughtworks.xstream.mapper.ClassAliasingMapper.realClass(ClassAliasingMapper.java:86)
at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:38)
at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:38)
at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:38)
at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:38)
at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:38)
at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:38)
at com.thoughtworks.xstream.mapper.ArrayMapper.realClass(ArrayMapper.java:96)
at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:38)
at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:38)
at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:38)
at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:38)
at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:38)
at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:38)
at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:38)
at com.thoughtworks.xstream.mapper.MapperWrapper.realClass(MapperWrapper.java:38)
at com.thoughtworks.xstream.mapper.CachingMapper.realClass(CachingMapper.java:56)
at com.thoughtworks.xstream.core.util.HierarchicalStreams.readClassType(HierarchicalStreams.java:29)
at com.thoughtworks.xstream.converters.collections.AbstractCollectionConverter.readItem(AbstractCollectionConverter.java:70)
at hudson.util.CopyOnWriteList$ConverterImpl.unmarshal(CopyOnWriteList.java:184)
at hudson.util.DescribableList$ConverterImpl.unmarshal(DescribableList.java:224)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convert(TreeUnmarshaller.java:82)
at com.thoughtworks.xstream.core.AbstractReferenceUnmarshaller.convert(AbstractReferenceUnmarshaller.java:63)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:76)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:60)
at hudson.util.RobustReflectionConverter.unmarshallField(RobustReflectionConverter.java:261)
at hudson.util.RobustReflectionConverter.doUnmarshal(RobustReflectionConverter.java:221)
at hudson.util.RobustReflectionConverter.unmarshal(RobustReflectionConverter.java:172)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convert(TreeUnmarshaller.java:82)
at com.thoughtworks.xstream.core.AbstractReferenceUnmarshaller.convert(AbstractReferenceUnmarshaller.java:63)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:76)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:60)
at com.thoughtworks.xstream.core.TreeUnmarshaller.start(TreeUnmarshaller.java:137)
at com.thoughtworks.xstream.core.AbstractTreeMarshallingStrategy.unmarshal(AbstractTreeMarshallingStrategy.java:33)
at com.thoughtworks.xstream.XStream.unmarshal(XStream.java:923)
at hudson.util.XStream2.unmarshal(XStream2.java:70)
at com.thoughtworks.xstream.XStream.unmarshal(XStream.java:909)
at com.thoughtworks.xstream.XStream.fromXML(XStream.java:853)
at hudson.XmlFile.read(XmlFile.java:126)
at hudson.model.Items.load(Items.java:106)
at hudson.model.Hudson$12.run(Hudson.java:2091)
at org.jvnet.hudson.reactor.TaskGraphBuilder$TaskImpl.run(TaskGraphBuilder.java:146)
at org.jvnet.hudson.reactor.Reactor.runTask(Reactor.java:259)
at hudson.model.Hudson$3.runTask(Hudson.java:642)
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:619)
failed to locate class: com.thoughtworks.xstream.mapper.CannotResolveClassException: hudson.plugins.checkstyle.CheckStyleResultAction : hudson.plugins.checkstyle.CheckStyleResultAction
failed to locate class: com.thoughtworks.xstream.mapper.CannotResolveClassException: hudson.plugins.checkstyle.CheckStyleResultAction : hudson.plugins.checkstyle.CheckStyleResultAction
failed to locate class: com.thoughtworks.xstream.mapper.CannotResolveClassException: hudson.plugins.checkstyle.CheckStyleResultAction : hudson.plugins.checkstyle.CheckStyleResultAction
failed to locate class: com.thoughtworks.xstream.mapper.CannotResolveClassException: hudson.plugins.checkstyle.CheckStyleResultAction : hudson.plugins.checkstyle.CheckStyleResultAction
failed to locate class: com.thoughtworks.xstream.mapper.CannotResolveClassException: hudson.plugins.checkstyle.CheckStyleResultAction : hudson.plugins.checkstyle.CheckStyleResultAction
failed to locate class: com.thoughtworks.xstream.mapper.CannotResolveClassException: hudson.plugins.checkstyle.CheckStyleResultAction : hudson.plugins.checkstyle.CheckStyleResultAction
failed to locate class: com.thoughtworks.xstream.mapper.CannotResolveClassException: hudson.plugins.checkstyle.CheckStyleResultAction : hudson.plugins.checkstyle.CheckStyleResultAction
failed to locate class: com.thoughtworks.xstream.mapper.CannotResolveClassException: hudson.plugins.checkstyle.CheckStyleResultAction : hudson.plugins.checkstyle.CheckStyleResultAction
failed to locate class: com.thoughtworks.xstream.mapper.CannotResolveClassException: hudson.plugins.checkstyle.CheckStyleResultAction : hudson.plugins.checkstyle.CheckStyleResultAction
failed to locate class: com.thoughtworks.xstream.mapper.CannotResolveClassException: hudson.plugins.checkstyle.CheckStyleResultAction : hudson.plugins.checkstyle.CheckStyleResultAction
failed to locate class: com.thoughtworks.xstream.mapper.CannotResolveClassException: hudson.plugins.checkstyle.CheckStyleResultAction : hudson.plugins.checkstyle.CheckStyleResultAction