This can happen, if you're using different EntityManager Instances. For example my case was: Method in SLSB called by Event (Observer) uses EntityManager and calls other SLSB Method which uses EntityManager as well, both per @In For some reason, both EntityManagers managed their own PersistenceContext, so when I deleted something in the second one, the Commit in the outer mehtod throws exactly this execption. took me three days to figure out. Not sure if this is a bug... Greetz GHad View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4109800#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...