It seems for me like a problem with the DEFAULT the classpath and/or included jars, which ECLIPSE 3.2 per default sets for the test-client. If i manually add all necessary jars of jboss to my test client project, then programm will run ok. But if i let eclipse determine the classpath (via Button "default"), the above error will thrown. Remember: This misbehaivor only occurs with jboss 4.20CR1 release of march 07, NOT with svn-checkout of november 06. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4027146#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...