I've got exactly the same problem, running on JBoss 5.0.0.Beta.
This answer seems to suggest, you could use jboss client stack instead of jwsdp:
Did you find any other solution to the problem?
Depending on how your client is packaged (EAR, JAR, WAR), you could scope your deployment to prevent this, but as mentioned, the best alternative would be to use JBossWS instead.
You should only deploy portable artifacts (i.e. beans, mapping.xml)
Scan the generated output for com.sun. you won't need any of those