remote server returned an error: (404) Not Found. while importing yahoo Contacts

private void RetriveContacts()
{
OAuthBase oauth = new OAuthBase();

Uri uri = new Uri("http://social.yahooapis.com/v1/user/" + OauthYahooGuid + "/contacts?format=XML");
string nonce = oauth.GenerateNonce();
string timeStamp = oauth.GenerateTimeStamp();
string normalizedUrl;
string normalizedRequestParameters;
string sig = oauth.GenerateSignature(uri, ConsumerKey, ConsumerSecret, OauthToken, OauthTokenSecret, "GET", timeStamp, nonce, OAuthBase.SignatureTypes.HMACSHA1, out normalizedUrl, out normalizedRequestParameters);

StringBuilder sbGetContacts = new StringBuilder(uri.ToString());

//Response.Write("URL: " + sbGetContacts.ToString());
//Response.End();

try
{
string returnStr = string.Empty;
HttpWebRequest req = (HttpWebRequest)WebRequest.Create(sbGetContacts.ToString());
req.Method = "GET";

string authHeader = "Authorization: OAuth " +
"realm=\"yahooapis.com\"" +
",oauth_consumer_key=\"" + ConsumerKey + "\"" +
",oauth_nonce=\"" + nonce + "\"" +
",oauth_signature_method=\"HMAC-SHA1\"" +
",oauth_timestamp=\"" + timeStamp + "\"" +
",oauth_token=\"" + OauthToken + "\"" +
",oauth_version=\"1.0\"" +
",oauth_signature=\"" + HttpUtility.UrlEncode(sig) + "\"";

//Response.Write("</br>Headers: " + authHeader);

req.Headers.Add(authHeader);
HttpWebResponse res = (HttpWebResponse)req.GetResponse();
StreamReader streamReader = new StreamReader(res.GetResponseStream());
returnStr = streamReader.ReadToEnd();
XmlDocument xmldoc = new XmlDocument();
xmldoc.LoadXml(returnStr);
XmlNodeList elemList = xmldoc.DocumentElement.GetElementsByTagName("fields");

ArrayList emails = new ArrayList();
for (int i = 0; i < elemList.Count; i++)
{
if (elemList[i].ChildNodes[1].InnerText == "email")
emails.Add(elemList[i].ChildNodes[2].InnerText);
//Response.Write(elemList[i].ChildNodes[2].InnerText + "<br/>");
}
grvMyFriends.DataSource = emails;
grvMyFriends.DataBind();
}
#region error
catch (WebException ex)
{
//Response.Write(ex.Message);
Response.Write("<br/>" + ex.Message + "</br>xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx");
Response.Write("<br/>length: " + ex.Source.Length.ToString());
Response.Write("<br/>stack trace: " + ex.StackTrace);
Response.Write("<br/>status: " + ex.Status.ToString());
HttpWebResponse res = (HttpWebResponse)ex.Response;
int code = Convert.ToInt32(res.StatusCode);

Response.Write("<br/>Status Code: (" + code.ToString() + ") " + res.StatusCode.ToString());
Response.Write("<br/>Status Description: " + res.StatusDescription);

if (ex.InnerException != null)
{
Response.Write("<br/>innerexception: " + ex.InnerException.Message);
}

if (ex.Source.Length > 0)
Response.Write("<br/>source: " + ex.Source.ToString());

if (res != null)
{
for (int i = 0; i < res.Headers.Count; i++)
{
Response.Write("<br/>headers: " + i.ToString() + ": " + res.Headers[i]);
}
}
}
#endregion error
}

This is the method i used...