ClassCastException running webservice from Portal Application

Hello,

i got a problem with consuming a webservice from a portal application to runtime:

A test to consume the same webservice via the same webservice proxy from a servlet (as described there: Link: [https://www.sdn.sap.com/irj/sdn/go/portal/prtroot/docs/library/uuid/0cac0dea-0d01-0010-edb4-8c7b068f4677] finish succesful.

I got a ClassCastException when trying to cast like this:

NotesGetNABUSER_DataService nabws = (NotesGetNABUSER_DataService) in.lookup("wsclients/proxies/sap.com/Domino_Web_Service_Proxy/com.sap.lotus.employeeProxy");

I add a private sharing reference to the portalapp.xml:

<application>
  <application-config>
    <property name="PrivateSharingReference" value="com.sap.portal.htmlb,SAPJ2EE::sap.com/Domino_Web_Service_Proxy"/>
  </application-config>

and also add the webservice proxy jar (found on server) file as external lib in several folders: Portal-INF/lib, Portal-INF/private/lib, Portal-INF/srclib.api and Portal-INF/srclib.core

Any suggestions?

Regards Henry