I noticed a similar problem using Hibernate 3.x with JBoss 6.x and 7.x. The problem was that Hibernate and the JEE 3.0 spec use annotations of the same name. Because JBoss is configured to automatically scan for JEE (in this case JPA) annotations, JBoss mis-interpreted the Hibernate annotations as JPA. We used the jboss-scanning.xml hack to disable JBoss' JEE annotations scanning, and that allowed us to use Hibernate. Could this be the same issue you're running into?