thanks for the reply. but it doesn't look like a 'permgen size' problem for me either. i maintained a list of jbpm process instance in the class as i posted above. and i displayed the list in the web page, with each entry in the list followed by a 'view detail' button. Clicking on the button leads to the display of the information associated to the specific process instance. if i switch between the instances too quickly, it (the exception) happens quite a lot -- at least one out of 8 clicks. if i don't do this 'crazy switching', it doesn't happen frequently -- maybe several times a day. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4071039#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...