Issue with Local Debug in VS 2013 (HTTP Error 401.0 - Unauthorized)

I found a strange issue and I'm not sure how to solve it.

I pulled a solution from TFS on both my Desktop and Laptop.

On both, when I debug the solution in VS 2013, I get the following error:

HTTP Error 401.0 - Unauthorized You do not have permission to view this directory or page.

The same code runs properly in VS 2012.

On the Desktop, if I debug it in VS 2012 first, then stop debugging I can debug successfully in VS 2013 until I close VS 2012.

On the laptop, if I try the same trick, I get an error that VS is unable to launch the IIS Express Web server because the port is already in use.

So it seems that when I debug in VS 2012 some credentials are being passed that are not being passed in VS 2013 (I'm guessing because of some change in the way this is handled?).

So what changed, and how can I update the solution so that VS 2013 can debug without first debugging in VS 2012?

NOTE: I've also asked this question at StackOverflow here