I had this problem and fixed it. Before and EJB gets passivated, everything is serialized. Make sure your objects can be fully serialized - especially non-EJB beans that you create within your EJB. Also be sure to close any 'connections to external resources' you have open, if any. While you are developing, it's useful to define @PrePassivate, @PostActivate etc. methods w/ simple System.out.println statements so you can monitor the lifecycle events w/out creating a mountain of trace info. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4027406#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...