Because of a current (JBoss 4.0.1) bug in the webservice deployer (web.xml is "corrected" be the deployer) you should
use packaged war files only! If you don't you will get 

- an "Already registered" Exception when redeploying your war component
- MethodNotKnown Exeption when calling the webservice method from the client

Cheers

Thomas Frey