Be careful having virtual directories overlapping MVC controllers in ASP.NET

Just wasted a bunch of time looking at a problem which, initially pointed at a permissions problem in our good old friend IIS7…

The error we got was a 500.19 error with the message:

The requested page cannot be accessed because the related configuration data for the page is invalid.

Well that’s a red herring. It turned out we had a Virtual Directory set up with the same name as an MVC controller – removing that sorted everything out!