setProperty must be overridden by all subclasses of SOAPMessage

Have you gotten this error message? Then you probably either upgraded from Java 5 to Java 6 in JBoss application, or you just tried to run your webservice client for the first time.

The reason your Webservice client call suddenly fails is because of a bug in JBoss WS with JBoss 4.x

I haven't tested this on JBoss 5, so I cannot for sure exclude this bug in JBoss 5. However, the bug seem to be fixed in jbossws-2.0.

The solution to this problem is to

Copy the three jars from <JBOSS_HOME>\server\default\lib to <JBOSS_HOME>\lib\endorsed.

jboss-jaxrpc.jar
jboss-jaxws.jar
jboss-saaj.jar 

More information can be found here