Ok, I solved it by myself. It would be rude, not to tell you, what was wrong! I dunno what excatly I've made wrong, when I build my programm, but the problem was my chosen transaction-strategy in persistence.xml - I'd chosen JTA. I googled a lot and found this: http://www.abcseo.com/tech/java/jboss-ebj-troubleshooting Search for anonymous wrote : JTA Transaction Manager I have tagged a class @Stateless and it works all fine in application context (without those ear stuff and the db-connection divided from the rest of the application) but there was the problem. I did everything like they shown in this solvement and added this property <property name="hibernate.transaction.manager_lookup_class" value="org.hibernate.transaction.JBossTransactionManagerLookup"/> to the property section in the persistence.xml Now everything working fine! Thank you anyway... BGMF View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4090954#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...