An error occurred when verifying security for the message

                   Core2ServiceHTTPSBASICHTTP2 service = new Core2ServiceHTTPSBASICHTTP2();
                COREEnvelopeRealTimeRequest request = new COREEnvelopeRealTimeRequest();
                COREEnvelopeRealTimeResponse response = new COREEnvelopeRealTimeResponse();

                request.CORERuleVersion = "2.2.0";
                request.Payload = sX12;
                request.PayloadID = "f81d4fae-7dec-11d0-a765-00a0c91e6bf6";
                request.PayloadType = "X12_270_Request_005010X279A1";
                request.ProcessingMode = "RealTime";
                request.ReceiverID = "my-reciever-id";
                request.SenderID = "my-sender-id";
                request.TimeStamp = "2007-08-30T10:20:34Z";
                
                

                service.Credentials = new System.Net.NetworkCredential("my-user-name", "my-password");
                response = service.RealTimeTransaction(request);  //this line throwing exception
//it is web service method.

//Exception Text : An error occurred when verifying security for the message

//when i use feddler and check request response then in request my credential is not going to WebService, 

//if you understand issue then please post your solution.

//waiting...

//Thanks in Advance