Web Request help C#

Hello,

What I am trying to do is use YouTube API in order to gather some susbscription information (see http://code.google.com/apis/youtube/2.0/developers_guide_dotnet.html#Retrieving_a_Subscription)

So what I do is:
   string url = "http://gdata.youtube.com/feeds/api/users/" + TUsername + "/subscriptions";
            WebRequest request;        
                     
           try
            {
                Application.DoEvents();
                request = WebRequest.Create(url);
                string usernamePassword = TUsername + ":" + TPassword;
                CredentialCache mycache = new CredentialCache();
                mycache.Add(new Uri(url), "Basic", new NetworkCredential(TUsername, TPassword));
                request.Credentials = mycache;
                request.Headers.Add("Authorization", "Basic " + Convert.ToBase64String(new ASCIIEncoding().GetBytes(usernamePassword)));

                WebResponse response = request.GetResponse();
                Stream receiveStream = response.GetResponseStream();
                StreamReader reader = new StreamReader(receiveStream, Encoding.UTF8);
                content = reader.ReadToEnd();

But it returns me 401 unauthorized error...

Im new to YouTube API, so please help me what I am doing wrong...!