Thanks for the response Keith. There are no client-side certificates involved here. I thought I was passing my credentials via the StreamWriter (some context-sensitive code had to be snipped in my example, but the "login=abc" was still there), but I take it they have to be passed by the WebRequest object rather than manually.

Thanks again for the help. I can't wait to try it out.

>Depending on the service provider, you will have to use your network credentials or a client certificate to connect to the resource. For network credentials, add webReq.Credentials = System.Net.CredentialCache.DefaultCredentials to the other statements that are setting the properties of the HttpWebRequest.