I have fiddler installed and I'm running an MVC3 app through visual studio. Whenever I try to hit the MVC page with fiddler (localhost:28267) I get a 401. How can I determine what's causing this? The page loads fine through IE/VS.
401 means that Fiddler fails to properly negotiate NTLM credentials. Check it with Firebug network console, you'll probably get the same behavior.