HttpWebRequest and strange networking errors

[cjb110]

I've got the following code that did seem to be working successfully: (It's sending a SOAP envelope to a Java web service and receiving a response) EndPoint is just a string property containing the URL and path to the WebService, Response is a HttpWebResponse property, that other classes use to process the response SOAP.

        //create the request
        HttpWebRequest req = (HttpWebRequest) WebRequest.CreateDefault(new Uri(EndPoint));
        //and request header info
        req.ContentType = "text/xml; charset=utf-8";
        req.Method = "POST";
        req.Accept = "text/xml";
        req.KeepAlive = false;
        req.Timeout = Timeout;
        req.Proxy = WebRequest.GetSystemWebProxy();

        req.Headers.Add("SOAPAction", EndPoint);

        //write the SOAP Message to the request
        using (StreamWriter stm = new StreamWriter(req.GetRequestStream(), Encoding.UTF8))
        {
            stm.Write(soapRequest.ToString(SaveOptions.DisableFormatting)); //remove the formatting from the passed XML.
            stm.Flush();
        }

        Response = null;
        try
        {
            //get the response
            Response = ((HttpWebResponse) req.GetResponse());
            //read the raw response into ResponseString
            using (StreamReader reader = new StreamReader(Response.GetResponseStream(), Encoding.UTF8))
                ResponseString = reader.ReadToEnd();
        }
        catch (WebException we)
        {
            throw new ApplicationException("A web exception occurred in calling Transact OUG!\\r\\n" + we.Message, we);
        }
        catch (Exception e)
        {
            throw new ApplicationException("A general exception occurred when calling Transact OUG!\\r\\n" + e.Message, e);
        }
        finally
        {
            if (Response != null)
                Response.Close();

            req = null;
        }

Now I'm not sure what's really changed but I'm getting really odd errors like 'An operation was attempted on something that is not a socket', now I think this might be threading related. As I'm seeing the very first time it returns a timeout, its only the second attempts that I get the odder errors. As I said this code was working fine when it was called via a single Window WPF app, I