Yes... this is http://jira.jboss.com/jira/browse/JBREM-649 There is a hashMap on Lease... Lease sends the hashMap to the server side by serialization. If the map changes while the serialization happens.. I mean... if there is a new client connecting... a ConcurrentModificationException happens breaking the IO. Remoting added synchronized to some blocks to avoid the concurrency. This bug would also happen under regular java serialization. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4003951#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...