I'm not well versed in C#, but you may want to remove the credentials from your url and include them as described here: http://msdn.microsoft.com/en-us/library/system.net.networkcredential%28v=vs.110%29.aspx
For example:
WebRequest request = WebRequest.Create("http://www.contoso.com/");
request.Credentials = CredentialCache.DefaultCredentials;