testing the webservices scenario, error

Hi experts,

We have a scenario, web<-->PI<-->RFC, i have created the interface and registered the service in SR.

When i am trying to test the scenario from the SR, i am getting the error below from the 'Web Services Navigator'

Web service returned error. Fault Code: "(http://schemas.xmlsoap.org/soap/envelope/)Server" Fault String: "Server Error"

In the monitoring, I can see the error below for the SOAP channel:

SOAP: Call failed: com.sap.engine.interfaces.messaging.api.exception.MessagingException: java.lang.NullPointerException: while trying to invoke the method com.sap.engine.interfaces.messaging.api.Payload.getInputStream() of an object returned from com.sap.aii.adapter.xi.ms.XIMessage.getMainPayload()

I believe this error is coz the SOAP channel is not able to invoke the mapping itself or even convert the input to the source message.

I don't know hw to go around debugging the scenario. I have tested the rfc and part functionality by creating a test scenario file-->pi-->rfc and it is invoking the rfc and generating the output for the value range passed.

Please help in removing this error or at least understanding it.

--

rgds

Shubhnam