After deploying a seam application which has dependencies on other projects and external jars this error appears when asking starting, publishing, cleanning, etc.:
Publishing failed
Could not publish to the server.
org.eclipse.wst.server.core.internal.ModuleFolder
Could not publish to the server.
org.eclipse.wst.server.core.internal.ModuleFolder

And this is the error log:
java.lang.ClassCastException: org.eclipse.wst.server.core.internal.ModuleFolder
at org.eclipse.jst.j2ee.internal.deployables.J2EEFlexProjDeployable.members(J2EEFlexProjDeployable.java:203)
at org.eclipse.wst.server.core.internal.ModulePublishInfo.fillCache(ModulePublishInfo.java:283)
at org.eclipse.wst.server.core.internal.ModulePublishInfo.getDelta(ModulePublishInfo.java:333)
at org.eclipse.wst.server.core.internal.ServerPublishInfo.getDelta(ServerPublishInfo.java:360)
at org.eclipse.wst.server.core.internal.Server.getPublishedResourceDelta(Server.java:1057)
at org.eclipse.wst.server.core.model.ServerBehaviourDelegate.getPublishedResourceDelta(ServerBehaviourDelegate.java:547)
at org.eclipse.wst.server.core.model.ServerBehaviourDelegate.publish(ServerBehaviourDelegate.java:613)
at org.eclipse.wst.server.core.internal.Server.doPublish(Server.java:887)
at org.eclipse.wst.server.core.internal.Server.publish(Server.java:874)
at org.eclipse.wst.server.core.internal.PublishServerJob.run(PublishServerJob.java:72)
at org.eclipse.core.internal.jobs.Worker.run(Worker.java:55)

After this error, the only way to start the jboss within the developer studio is removing the server and adding it again. But the error appears later again.

This bug seems to be fixed in WTP 2.0.3:
https://bugs.eclipse.org/bugs/show_bug.cgi?id=233196

Is it possible to upgrade WTP version?