So you get your web service client working nicely and deploy your code to Websphere only to find this ugly Websphere Exception:

[6/3/10 21:28:28:081 EDT] 00000035 Connection    E com.ibm.ws.webservices.engine.client.Connection invoke WSWS3227E:  Error: Exception:
java.lang.IllegalArgumentException: argument type mismatch

From what I have read online, this can happen based on the webservices.jar file not being the most current one.  I didn’t have that issue though, but what I did find was how Websphere’s classloader can cause this exception.  I had setup a SharedLib for my new webservice JAR files but what I should have done was to include the JAR with my WAR file’s WEB-INF/lib and remove the entry from the Shared Lib.  This seemed to fix this.