The problem is critical, because after this exception application stops to function : button that invokes component method simply does not do that anymore. Please post at least any thoughts if not solutions. Does any library use these "Drools" implicitly ? Seam core, Seam remoting, JBoss EJB3 ? How is it possible that application is looking for org.drools.WorkingMemory class upon passivation ? In order to exclude the influence of previously deployed applications, I installed another instance of JBoss from scratch. The same effect. Tried JBoss 4.0.5 and 4.2.1. Seam version is 1.2.1GA. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4081847#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...