You'll get this error if your RC9 installation wasn't over a server configuration using clustering. From http://wiki.jboss.org/wiki/Wiki.jsp?page=FromRC8RC9: anonymous wrote : If you are patching a server configuration other than one using clustering from the "all" configuration from the JEMS Installer, you must remove ejb3-clustered-sfsbcache-service.xml and ejb3-entity-cache-service.xml as they'll be unable to find org.jboss.cache.TreeCache. Had this error when first going to RC9 as well. :) S, ALR View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=3979420#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...