Got solution!!! The relevant class (org.hibernate.MappingNotFoundException) was added to Hibernate in version 3.2.0.cr3 or 3.2.0.cr4. The version that comes with the EJB3 RC9 is cr4. The version I had in the JBossAS is cr2, which lacked that file. The EJB3 ant installer should have copied the new version to the JBossAS, but unfortunately the time stamp of the JBossAS jars was newer than the EJB3, so ant has ignored the copy request. My solution was simple - I've used "touch" to update the timestamp of the EJB3 jars, and then they were copied correctly. Another option is to add the attribute overwrite="true" to the copy commands. David View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=3991341#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...