Are you using seam 1.2.1 with richFaces/ajax4Jjsf enabled? I suffer from very similar problems. Randomly I get exceptions like your exception or exceptions like this one: "Cannot get value for expression '#{org.jboss.seam.messages}' " After I switched off ajax4jsf by commenting out the ajax4jsf filter and the ajax4jsf.VIEW_HANDLERS within web.xml and reactivating the view-handler within faces-config.xml the problem disapears. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4047223#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...