HttpWebRequest and System.Net.CredentialCache

My code creates an HttpWebRequst, assigns credentials, waits for a response, then if the response is valid displays an image. The code works correcly if I run it in visual studio where the url is something like http://localhost:2522/, but if I actually navigate to my machine using my ip address and folder where the application is, the response is not valid and the code falls to the catch below. Do you know how I could get this to work so that it works when I actually navigate to the site instead of just running it in visual studio?  Thanks:

  1 // Directory settings is IIS for default web site must be Windows Authentication
2 HttpWebResponse response = null;
3 string imageURL = " ...