XML : RESTFul XML Service sending (401) Unauthorized Error

I've been trying to use a RESTful XML service that brings back extra data on a search using names or last names. The way I am suppose to authenticate is by using a separate REST API request that gives me access to the rest of the services. But by the time I call the second request it sends me the following error. "The remote server returned an error: (401) Unauthorized.". The user and password that I'm using are the correct ones so I'm a bit stuck on why this message is being sent.

  using System.Net;   using System.IO;   using System.Xml;   using System.Xml.XPath;    private void btnSearch_Click(object sender, EventArgs e) {      string sURL, aURL;      sURL = "http://url.com/data/qws/access?var1=user&var2=password";      aURL = "http://url.mx/data/qws/pepsp?name=miguel&lastname=osorio";        CookieContainer cookieQ = new CookieContainer();       HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create(sURL);      request.CookieContainer = cookieQ;        HttpWebResponse response = (HttpWebResponse)request.GetResponse();      request = (HttpWebRequest)HttpWebRequest.Create(aURL);      request.CookieContainer = cookieQ;      response = (HttpWebResponse)request.GetResponse();        using (response) {          XmlDocument xmlDoc = new XmlDocument();          xmlDoc.Load(response.GetResponseStream());          XmlNode name = xmlDoc.SelectSingleNode("/xml/person/name");          XmlNode lastname = xmlDoc.SelectSingleNode("/xml/person/lastname");          MessageBox.Show(name.InnerText + ' ' + lastname.InnerText);      }  }