Upps, it was not the full reply. Two user got this exception at 16:40:47. Small implementation detail: We use in our application Hibernate Search. When an user types something in a search field, we start searching in a background thread. When the user continues to type in the search field, we start another thread and interrupt the first one when it is not finished. Hence the client may invoke one and the same method of a session bean multiple times in a minute. But the exception occurs not only on search. It occurs also when invoking other methods. ron.sigal(a)jboss.com wrote : | | ... | If that's the only reason for enabling connection checking, you might want to take it out, since it will introduce extra latency and network traffic. | Yes, this was our guess. Thanks for the tip. We will take it out. Thanks in advance and best regards, Andrej View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4185622#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...