Is there a special security configuration that is needed to get a SQL server call to work correctly thru a SOAP Web service?

I can sucessfully call all web methods that do not query data thru the Web Service. I can sucessfully call all Data Requests thru COM (DLL) directly. But, I cannot get any records from the same request to the data methods in that same DLL called as a Soap Service. This uses a DSN that is passed the UID and Password.