When using Jboss Tools's "Generate Entities", a ClassCastException occurs and the entities cannot be generated when clicking on the "Finish" button (see screenshot).
The exception message is: "org.hibernate.tool.hbm2x.ExporterException: Exception when instantiating tool hibernatetool.util.toolclass with org.hibernate.eclipse.launch.SeamUtil".
The root cause seems that the org.hibernate.eclipse.launch.SeamUtil class could not be found (ClassNotFoundException).

In JBossTools-ALL-win32-3.0.1.GA-R200905070146-H18.zip, there was a SeamUtil class in "eclipse\plugins\org.hibernate.eclipse_3.2.4.GA-R200905070146-H18\org.hibernate.eclipse.jar\org\hibernate\eclipse\launch\"

In JBossTools-ALL-win32-3.1.0.M2-N200906241801-H293.zip, this is not the case anymore: the "launch" package is no more in "eclipse\plugins\org.hibernate.eclipse_3.3.0.M2-N200906241801-H293\org.hibernate.eclipse.jar\org\hibernate\eclipse\"

Since there is a workaround, I set the severity to "Critical" rather than "Blocker".