Problem resolved by setting an additional instance variable to null in the @PrePassivate method: private void cleanUp() | { | try | { | if (rs != null) | { | rs.close(); | } | if (preparedStmt != null) | { | preparedStmt.close(); | } | if (stmt != null) | { | stmt.close(); | } | if (con != null) | { | con.close(); | } | | } | catch(SQLException e) { | e.printStackTrace(); | } | } | | @PrePassivate | private void cleanupBeforePassivation() { | | cleanUp(); | con = null; | stmt = null; | preparedStmt = null; | rs = null; | | params = null; //<-- root cause identified! at least this variable not being set to null causes the | // javax.ejb.EJBException: Could not passivate; failed to save state error... | } Alternative fix is to not use the Map params variable as an instance variable, but as multiple local instances. The stack trace is very misleading: anonymous wrote : Caused by: java.lang.NoClassDefFoundError: org/jaxen/VariableContext | when that class is actually residing in the JBOSS_HOME/server/default/lib/jaxen.jar... View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4144672#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...