Authentication dialog when running with Visual Studio web server

When using Visual Studio’s built in web server, every time I make a page request the standard login box pops up and asks for credentials. It doesn’t work if I actually put in my credentials, so I just have to hit cancel 5 times so it will go away.

When I run the application through IIS (locally or on test server) it works just fine (no login box comes up).

Anyone know how to fix this or have any idea what might be causing it?