Hi JBM experts: After change the security policy setting from permission java.util.PropertyPermission "*", "read"; to permission java.util.PropertyPermission "*", "read,write"; The NoClassDefFoundError is gone and now I am getting the following exception when trying to do: connection = connectionFactory.createConnection(); org.jboss.jms.exception.MessagingNetworkFailureException: Failed to download and/or install client side AOP stack at org.jboss.jms.client.delegate.ClientClusteredConnectionFactoryDelegate.org$jboss$jms$client$delegate$ClientClusteredConnectionFactoryDelegate$getClientAOPStack$aopClientClusteredConnectionFactoryDelegate.java:250) at org.jboss.jms.client.delegate.ClientClusteredConnectionFactoryDelegate.getClientAOPStack(ClientClusteredConnectionFactoryDelegate.java) at org.jboss.jms.client.ClientAOPStackLoader.loadClientAOPStackLoader.java:75) at g.jboss.jms.client.JBossConnectionFactory.createConnectionInternal(JBossConnectionFactory.java:192) This exception is somewhat generic and therefore I am posting here to see if anyone can share some of the common cause for this exception. Again, thanks for those of you kindly share your knowledge and ideas. View the original post : http://www.jboss.org/index.html?module=bb&op=viewtopic&p=4226078#... Reply to the post : http://www.jboss.org/index.html?module=bb&op=posting&mode=reply&a...