Cannot find child element: arg0

hi,
I am trying to run a web service.
The Java client runs without any problem.
But I have tried 2 clients: one in PHP, the other one with VBS, and both 
give me the error "Cannot find child element: arg0"

Here is the code
Echo.java

  code:
------------------------------------------------------------------------------

package uk.co.regdeveloper.webservice; import java.rmi.Remote; import 
javax.jws.WebParam;import javax.jws.WebService;import 
javax.jws.soap.SOAPBinding; @WebService@SOAPBinding(style = 
SOAPBinding.Style.RPC, use = SOAPBinding.Use.LITERAL)//@SOAPBinding(style = 
Style.DOCUMENT)public interface Echo extends Remote {        String 
echo(@WebParam(name="MonParam") String e);}
------------------------------------------------------------------------------



EchoBean.java

  code:
------------------------------------------------------------------------------

package uk.co.regdeveloper.webservice; import javax.ejb.Local;import 
javax.ejb.Stateless;import javax.jws.WebParam;import 
javax.jws.WebService;import javax.jws.soap.SOAPBinding; 
@Stateless@WebService(endpointInterface = 
"uk.co.regdeveloper.webservice.Echo")@SOAPBinding(style = 
SOAPBinding.Style.RPC, use = 
SOAPBinding.Use.LITERAL)@Local(Echo.class)public class EchoBean { 
public String echo(        		        		@WebParam(name="MyParam") String e) 
{                return "Web Service Echo + " + e;        }}
------------------------------------------------------------------------------



If i specify the name of the parameter with the @WebParam, then i get the 
same error message : "Cannot find child element: MyParam".

So i am using the RPC/LITERAL style, and I get the error "Cannot find child 
element: arg0"
If I use the DOCUMENT/LITERAL style, I get a different error.
Anyways, I am stuck here.
Does anyone have an idea ?
I know it is not PHP related, since I get the exact same error with a 
completely different client (VBS).

Thanks for helping