Login failed while calling WCF method from client ?

Question

Hi,

I have WCF(.svc) service and for calling WCF method i have created windows application. In windows appl i have added reference and call WCF method. It calling perfectly when method do not have database interaction but when method does have database interaction then it gives me below error-

Login Failed.The login is from an untrusted domain and cannot be used with windows authentication.

This method call database connection because method contain stored Procedure.

Please suggest if anybody have such experienced!!!!!