To reproduce:
1. Install Jenkins 1.516 which comes with bundled CVS Plugin 2.8
2. create a maven job using a CVS SCM and save it
3. downgrade CVS plugin to 1.6
4. restart jenkins

Result: the job neither isnt't available in the "all" view, nor cant it be displayed by opening a bookmark with the job URL

Expected: job is displayed at least in "all" view and can be called directly by using the job name URL, at least with an error message about non-supported plugin-data in the job

Workaround: remove the <scm> section from config.xml and restart Jenkinks and configure CVS with the previous values

In the log there a are lot of plugin-releated error messages:
Jun 23, 2013 11:12:46 AM hudson.util.RobustReflectionConverter doUnmarshal
WARNING: Skipping a non-existent field repositories
com.thoughtworks.xstream.converters.reflection.MissingFieldException: No field 'repositories' found in class 'hudson.scm.CVSSCM'
at com.thoughtworks.xstream.converters.reflection.FieldDictionary.field(FieldDictionary.java:94)
at com.thoughtworks.xstream.converters.reflection.PureJavaReflectionProvider.getFieldType(PureJavaReflectionProvider.java:157)
at hudson.util.RobustReflectionConverter.determineType(RobustReflectionConverter.java:399)
at hudson.util.RobustReflectionConverter.doUnmarshal(RobustReflectionConverter.java:271)
at hudson.util.RobustReflectionConverter.unmarshal(RobustReflectionConverter.java:222)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convert(TreeUnmarshaller.java:72)
at com.thoughtworks.xstream.core.AbstractReferenceUnmarshaller.convert(AbstractReferenceUnmarshaller.java:65)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:66)
at hudson.util.RobustReflectionConverter.unmarshalField(RobustReflectionConverter.java:333)
at hudson.util.RobustReflectionConverter.doUnmarshal(RobustReflectionConverter.java:275)
at hudson.util.RobustReflectionConverter.unmarshal(RobustReflectionConverter.java:222)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convert(TreeUnmarshaller.java:72)
at com.thoughtworks.xstream.core.AbstractReferenceUnmarshaller.convert(AbstractReferenceUnmarshaller.java:65)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:66)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:50)
at com.thoughtworks.xstream.core.TreeUnmarshaller.start(TreeUnmarshaller.java:134)
at com.thoughtworks.xstream.core.AbstractTreeMarshallingStrategy.unmarshal(AbstractTreeMarshallingStrategy.java:32)
at com.thoughtworks.xstream.XStream.unmarshal(XStream.java:1061)
at hudson.util.XStream2.unmarshal(XStream2.java:109)
at com.thoughtworks.xstream.XStream.unmarshal(XStream.java:1045)
at com.thoughtworks.xstream.XStream.fromXML(XStream.java:925)
at hudson.XmlFile.read(XmlFile.java:143)
at hudson.model.Items.load(Items.java:220)
at jenkins.model.Jenkins$17.run(Jenkins.java:2542)
at org.jvnet.hudson.reactor.TaskGraphBuilder$TaskImpl.run(TaskGraphBuilder.java:146)
at org.jvnet.hudson.reactor.Reactor.runTask(Reactor.java:259)
at jenkins.model.Jenkins$7.runTask(Jenkins.java:893)
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)
Jun 23, 2013 11:12:46 AM jenkins.InitReactorRunner$1 onTaskFailed
SEVERE: Failed Loading job uniqa-aura
hudson.util.IOException2: Unable to read /var/hudson/jobs/uniqa-aura/config.xml
at hudson.XmlFile.read(XmlFile.java:147)
at hudson.model.Items.load(Items.java:220)
at jenkins.model.Jenkins$17.run(Jenkins.java:2542)
at org.jvnet.hudson.reactor.TaskGraphBuilder$TaskImpl.run(TaskGraphBuilder.java:146)
at org.jvnet.hudson.reactor.Reactor.runTask(Reactor.java:259)
at jenkins.model.Jenkins$7.runTask(Jenkins.java:893)
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: com.thoughtworks.xstream.converters.ConversionException: Could not set field class hudson.scm.CVSSCM.skipChangeLog : null : Could not set field class hudson.scm.CVSSCM.skipChangeLog : null
---- Debugging information ----
message : Could not set field class hudson.scm.CVSSCM.skipChangeLog : null
cause-exception : com.thoughtworks.xstream.converters.reflection.ObjectAccessException
cause-message : Could not set field class hudson.scm.CVSSCM.skipChangeLog : null
class : hudson.scm.CVSSCM
required-type : hudson.scm.CVSSCM
converter-type : hudson.util.RobustReflectionConverter
path : /maven2-moduleset/scm/skipChangeLog
line number : 54
class[1] : hudson.maven.MavenModuleSet
version : null
-------------------------------
at com.thoughtworks.xstream.core.TreeUnmarshaller.convert(TreeUnmarshaller.java:79)
at com.thoughtworks.xstream.core.AbstractReferenceUnmarshaller.convert(AbstractReferenceUnmarshaller.java:65)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:66)
at hudson.util.RobustReflectionConverter.unmarshalField(RobustReflectionConverter.java:333)
at hudson.util.RobustReflectionConverter.doUnmarshal(RobustReflectionConverter.java:275)
at hudson.util.RobustReflectionConverter.unmarshal(RobustReflectionConverter.java:222)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convert(TreeUnmarshaller.java:72)
at com.thoughtworks.xstream.core.AbstractReferenceUnmarshaller.convert(AbstractReferenceUnmarshaller.java:65)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:66)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:50)
at com.thoughtworks.xstream.core.TreeUnmarshaller.start(TreeUnmarshaller.java:134)
at com.thoughtworks.xstream.core.AbstractTreeMarshallingStrategy.unmarshal(AbstractTreeMarshallingStrategy.java:32)
at com.thoughtworks.xstream.XStream.unmarshal(XStream.java:1061)
at hudson.util.XStream2.unmarshal(XStream2.java:109)
at com.thoughtworks.xstream.XStream.unmarshal(XStream.java:1045)
at com.thoughtworks.xstream.XStream.fromXML(XStream.java:925)
at hudson.XmlFile.read(XmlFile.java:143)
... 10 more
Caused by: com.thoughtworks.xstream.converters.reflection.ObjectAccessException: Could not set field class hudson.scm.CVSSCM.skipChangeLog : null
at com.thoughtworks.xstream.converters.reflection.Sun14ReflectionProvider.write(Sun14ReflectionProvider.java:141)
at com.thoughtworks.xstream.converters.reflection.Sun14ReflectionProvider.writeField(Sun14ReflectionProvider.java:104)
at hudson.util.RobustReflectionConverter.doUnmarshal(RobustReflectionConverter.java:290)
at hudson.util.RobustReflectionConverter.unmarshal(RobustReflectionConverter.java:222)
at com.thoughtworks.xstream.core.TreeUnmarshaller.convert(TreeUnmarshaller.java:72)
... 26 more
Caused by: java.lang.IllegalArgumentException
at sun.misc.Unsafe.objectFieldOffset(Native Method)
at com.thoughtworks.xstream.converters.reflection.Sun14ReflectionProvider.getFieldOffset(Sun14ReflectionProvider.java:150)
at com.thoughtworks.xstream.converters.reflection.Sun14ReflectionProvider.write(Sun14ReflectionProvider.java:112)
... 30 more