This is telling you that the JVM embedded within your browser is older than the JVM used to compile the Java code. If I recall correctly, version 48.0 is for code compiled with a 1.4 JVM, therefore the JVM in your browser must be 1.3. If you are running Firefox in Windows, you can open the Java Control Panel applet and change which JVM you are using. The other possibility is to install a 1.4.2 JVM (or higher), that should fix up Firefox. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4029874#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...