From the catalina.log (Tomcat 6):

SEVERE: Failed to record SCM polling
java.lang.ClassCastException: hudson.maven.MavenModuleSetBuild cannot be cast to
hudson.model.Build
at hudson.plugins.clearcase.ClearCaseSCM.pollChanges(ClearCaseSCM.java:134)
at hudson.model.AbstractProject.pollSCMChanges(AbstractProject.java:582)
at hudson.triggers.SCMTrigger$Runner.runPolling(SCMTrigger.java :260)
at hudson.triggers.SCMTrigger$Runner.run(SCMTrigger.java:292)
at java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source)
at java.util.concurrent.FutureTask$Sync.innerRun(Unknown Source)
at java.util.concurrent.FutureTask.run(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)

It happens when the Poll SCM scheduled task kicks in.

Environment:
Clearcase plugin: 2.1 (latest available release)
Hudson version: 144 (same problem with 156)