Sorry, I don't think deploying a 3.0.1 cache inside an AS 4.x clustered webapp war will work. :( As you've seen, the session replication code needs the 1.4.x classes, so you can't just replace the JBC version in server/all/lib. But if the 3.0.1 classes are in the war, they'll be visible to the session replication code as well, likely leading to incompatible type issue (e.g. which version or org.jboss.cache.Fqn). View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4199125#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...