XDoclet 1.2.2 that comes with MyEclipse does not support Hibernate 3.0 (only 1.1 and 2.0).
To make it working I removed all the jar files except org-jboss-ide-eclipse-xdoclet-core.jar in the com.genuitec.jboss.ide.eclipse.xdoclet.core_3.9.210 plugin, and replaced them with version 1.2.3 of xdoclet jars. For the moment everything seems to be working.
Will keep you posted once I run into problems.
regards
rp