I have updated Hudson from 1.279 to 1.312 and every time I start tomcat I have
the following exception in my log:

Jun 26, 2009 11:27:27 AM hudson.model.Hudson load
INFO: Took 5097 ms to load
Jun 26, 2009 11:27:27 AM hudson.TcpSlaveAgentListener <init>
INFO: JNLP slave agent listener started on TCP port 64825
Jun 26, 2009 11:27:35 AM hudson.util.RobustReflectionConverter doUnmarshal
WARNING: Skipping a non-existent field monitor
com.thoughtworks.xstream.converters.reflection.NonExistentFieldException: No
such field hudson.triggers.SCMTrigger$DescriptorImpl.monitor
at
com.thoughtworks.xstream.converters.reflection.FieldDictionary.field(FieldDictionary.java:106)
at
com.thoughtworks.xstream.converters.reflection.PureJavaReflectionProvider.getFieldType(PureJavaReflectionProvider.java:152)
at
hudson.util.RobustReflectionConverter.determineType(RobustReflectionConverter.java:327)
at
hudson.util.RobustReflectionConverter.doUnmarshal(RobustReflectionConverter.java:218)
at
hudson.util.RobustReflectionConverter.unmarshal(RobustReflectionConverter.java:173)
at
com.thoughtworks.xstream.core.TreeUnmarshaller.convert(TreeUnmarshaller.java:82)
at
com.thoughtworks.xstream.core.AbstractReferenceUnmarshaller.convert(AbstractReferenceUnmarshaller.java:63)
at
com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:76)
at
com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:60)
at
com.thoughtworks.xstream.core.TreeUnmarshaller.start(TreeUnmarshaller.java:137)
at
com.thoughtworks.xstream.core.AbstractTreeMarshallingStrategy.unmarshal(AbstractTreeMarshallingStrategy.java:33)
at com.thoughtworks.xstream.XStream.unmarshal(XStream.java:923)
at hudson.util.XStream2.unmarshal(XStream2.java:65)
at com.thoughtworks.xstream.XStream.unmarshal(XStream.java:909)
at hudson.XmlFile.unmarshal(XmlFile.java:146)
at hudson.model.Descriptor.load(Descriptor.java:486)
at hudson.triggers.SCMTrigger$DescriptorImpl.<init>(SCMTrigger.java:163)
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at
sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
at
sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
at java.lang.reflect.Constructor.newInstance(Constructor.java:494)
at java.lang.Class.newInstance0(Class.java:350)
at java.lang.Class.newInstance(Class.java:303)
at net.java.sezpoz.IndexItem.instance(IndexItem.java:149)
at hudson.ExtensionFinder$Sezpoz.findExtensions(ExtensionFinder.java:101)
at hudson.ExtensionList.load(ExtensionList.java:191)
at hudson.ExtensionList.ensureLoaded(ExtensionList.java:177)
at hudson.ExtensionList.iterator(ExtensionList.java:108)
at hudson.DescriptorExtensionList.load(DescriptorExtensionList.java:131)
at hudson.ExtensionList.ensureLoaded(ExtensionList.java:177)
at hudson.ExtensionList.iterator(ExtensionList.java:108)
at hudson.model.ComputerSet.<clinit>(ComputerSet.java:368)
at hudson.model.Hudson.getComputer(Hudson.java:1227)
at
hudson.model.LoadStatistics$LoadStatisticsUpdater.doRun(LoadStatistics.java:204)
at hudson.triggers.SafeTimerTask.run(SafeTimerTask.java:54)
at java.util.TimerThread.mainLoop(Timer.java:512)
at java.util.TimerThread.run(Timer.java:462)