I got the exception resolved by upgrading Jboss 4.0.5GA to latest EJB3 and JBosssCache 1.4.1SP2. http://www.jboss.com/index.html?module=bb&op=viewtopic&t=96095&am... http://jira.jboss.com/jira/browse/EJBTHREE-746 Gavin, I`ve read what the reference guide says about clustering, and if I`ve understood it correctly, the cause for the performance degradation is, that seam has to explicitely call .setAttribute as a workaround for servers where replication isn`t triggered by only a property change. If JBoss isn`t on the list of this buggy Servers (I have to find out), why not to have a configuration parameter, where we can explicitely set, if we want to use the workaround or not, defaulting to workaround=yes. Juraj Holtak View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4026212#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...