[closed] forbidden error creating workitem using OSLC

I'm trying to create a java client that can talk with RTC (4.0.3) via OSLC, to create/read/update WI.

Tthe "create" of a ChangeRequest (WI) fails.

The code  is:

//Create the change request
ClientResponse creationResponse = client.createResource(
                           changeRequestCreation, changeRequest,
                           OslcMediaType.APPLICATION_RDF_XML,
                           OslcMediaType.APPLICATION_RDF_XML);

String changeRequestLocation = creationResponse.getHeaders().getFirst(HttpHeaders.LOCATION);

You can realize that "create" fails since the "changeRequestLocation" is null.

The ClientResponse fields "status" and "message" are respectively "403" and "forbidden".

I'm sure that credentials are correct, and they are allowed to create a WI (I've verified from RTC WUI), someone can help me?

thanks!