Ошибка Expectation Failed при HttpWebRequest

HttpWebRequest authme = (HttpWebRequest)WebRequest.Create("http://pw.mail.ru/login.php?do=login");
                authme.Method = "POST";
                authme.CookieContainer = cooks;
                authme.Expect = "false";
                authme.Referer = "pw.mail.ru";
                authme.KeepAlive = true;
                authme.ProtocolVersion = HttpVersion.Version11;
                authme.ServicePoint.Expect100Continue = false;
                authme.Accept = "text/html, application/xml;q=0.9, application/xhtml+xml, image/png, image/webp, image/jpeg, image/gif, image/x-xbitmap, */*;q";
                authme.UserAgent = "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/535.11 (KHTML, like Gecko) Chrome/17.0.963.56 Safari/535.11";
                string authData = "s=&do=login&vb_login_md5password=" + getMd5Hash(password) + "&vb_login_md5password_utf=" + getMd5Hash(password) + "&vb_login_username=" + login + "&vb_login_password=" + password;
                byte[] sendData = Encoding.ASCII.GetBytes(authData);
                authme.ContentLength = sendData.Length;
                authme.Proxy = new WebProxy(ip, port);
                authme.ContentType = "application/x-www-form-urlencoded";
                authme.GetRequestStream().Write(sendData, 0, sendData.Length);
                authme.GetRequestStream().Close();
                authme.AllowAutoRedirect = false;
                HttpWebResponse response = (HttpWebResponse)authme.GetResponse();