hi carlo, thanks for the link. do you have that problem with a pure ejb app or with a web app using seam? i posted it in the seam forum too and gavin told me to set the timeout of the session scoped SFSBs to a value above the session timeout. i used the jboss annotation @CacheConfig and it worked. i'm not really sure if it's a bug. i hope someone could clarify this, is it a bug or just something special about arraylists or so? View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=3959918#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...