I tracked the problem within the debugger and found the source of the error. Obivously it is a different naming scheme they have in JBoss 5. Looking at the constructor of Hibernate's SessionFactoryImpl(), I saw the creation of a local variable named 'cacheRegionPrefix' (String cacheRegionPrefix = settings.getCacheRegionPrefix()), which is then later used as argument for a cache region name. Now, in JBoss this cacheRegionPrefix results into something like this: | persistence.unit:unitName=dpjwApp-ear-1.0.ear/dpjw-core-1.0.jar#dpjw_office. | whereas in JBoss 4.2.3 it was | dpjwApp-ear-1_0_ear,dpjw_office. | . Carlo Nice to see: BUT what can WE do here??? View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4195084#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...