We are experiencing EXACTLY the same problem with Apache 2.0 proxying requests to JBoss 4.0.5 using mod_proxy_ajp. I'd like to participate further in the discussion/resolution as this is a critical issue for us. Should this topic be opened under a different forum group? Or is Clustering/JBoss the right topic? 2007-05-09 10:36:05,645 INFO[org.jboss.web.tomcat.tc5.session.CacheListener] Possible concurrency problem: Replicated version id 50 matches -memory version for session ZyqAtRH+rizMxXjib4eMtA** Is this possibly a mod_proxy_ajp issue? We've successfully used mod_jk to proxy requests to JBoss in the past. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4044344#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...