I�m no JAXB expert, but this error might happen in different scenarios when jar files are not properly signed. An example could be when a class is located in two jars (and both are presented into the classpath), but only the second jar is signed. Now I don�t exactly remember but if switching the order in which the jars are loaded and having the signed jars loaded first might overcome the problem. Also is worth trying deploying those signed jars into the endorsed folder of the server runtime environment. Finally if nothing works, there is a very simple (although not always recommended) trick: usually the jars are signed using a special tool like jarsigner. In a nutshell this tool inserts two special files xxx.SF and xxx.RSA inside the jar in order to sign it. The trick is to remove those files from the jar and �unsigned� the jar. If you think this won�t bring any security concerns to your environment you might try it, but please don�t tell your manger I was the one that told you about it :-) I hope other people will advice you better. Regards.