I'm afraid the problem still exists. However, it was hidden for a while behind another serialization problem regarding java.lang.reflect.Method. Seems we/some of the frameworks we use are putting this into the Session. After searching for quite a long time I kind of gave up and just removed the exception from the log files by setting the log level to fatal. Not a very honorable thing to do, but I found that session replication and failover seems to work despite the problem, and that's what counts for me most. Regards Martin View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=3994039#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...