While the entities are all within the same navigation and request, you may get different entities due to entity manager flushes when queries are run. When you execute a query, it can flush the entity manager therefore invalidating the entity manager entity cache. For example : | MyClass a = entityManager.find(MyClass.class,id); | MyList = entityManager.createQuery("...").getResultList(); | MyClass b = entityManager.find(MyClass.class,id); | Here, I believe 'a' and 'b' would be different objects representing the same entity with the same id because the query caused a flush which invalidated the cache and caused the entity manager to create and load a new instance of the entity. What you could try, to diagnose the problem a bit is adding : | entityManager.save(a); | entityManager.save(b); | If one of them is a stale detached object, then the entity manager will complain. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4109597#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...