Error between SSRS and ASP.NET app: Cannot access a closed Stream.

Hello

We are trying to connect SSRS with an asp.net application.

But we get the following error: Cannot access a closed Stream.

We use the follow in code to access the report.

            string strReportUser = @"user";
            string strReportUserPW = "pwd";
            string strReportUserDomain = "";
            //Session["rp_DatePar"].ToString()
            DateTime DateNow = DateTime.ParseExact("15/05/2013", "dd/MM/yyyy", CultureInfo.InvariantCulture);
            string sTargetURL = "http://server/reportserver?%2f10139+-+Unibind+Scorecard&rs:Command=Render&rs:Format=PDF";

            HttpWebRequest req =
                  (HttpWebRequest)WebRequest.Create(sTargetURL);
            req.PreAuthenticate = true;
            //req.UseDefaultCredentials = true; 
            req.Credentials = new System.Net.NetworkCredential(
                strReportUser,
                strReportUserPW,
                strReportUserDomain);

            HttpWebResponse HttpWResp = (HttpWebResponse)req.GetResponse();

            Stream fStream = HttpWResp.GetResponseStream();

            HttpWResp.Close();



            //Now turn around and send this as the response..
            byte[] fileBytes = ReadFully(fStream);
            // Could save to a database or file here as well.

            Response.Clear();
            Response.ContentType = "application/pdf";
            Response.AddHeader("content-disposition","attachment; filename=\"ReportFor" +"test" + ".pdf\"");
            Response.BinaryWrite(fileBytes);
            Response.Flush();
            Response.End();
        }
        public static byte[] ReadFully(Stream input)
        {
            using (MemoryStream ms = new MemoryStream())
            {
                input.CopyTo(ms);
                return ms.ToArray();
            }
        }  

Can somebody tell us what is going wrong?

First we also had had an authentication error 401 I don't know how we fixed it but we are not getting that error again.

Kind Regards 

Matthias