Markus, Let's stick to JBoss-4.0.4 (i guess the book is based on that?). And let's stick to JDK-1.5 in all places (the client and the server). anonymous wrote : Caused by: java.io.InvalidClassException: org.jboss.ejb3.remoting.IsLocalInterceptor; local class in | compatible: stream classdesc serialVersionUID = 595045557897063404, local class serialVersionUID = - | 3758782076801249473 The exception that you are seeing is because of an incorrect version of jar file in your client classpath. Remove all the jar files from your client classpath and then include only the jbossall-client.jar which is present in the %JBOSS_HOME%\client folder of your JBoss-4.0.4 version of the server. Then rebuild your entire project with JDK 1.5 and deploy it to the server. Let us know how it goes. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4148601#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...