IIS 7.5 returns error 401 instead of 500

Question

I have a strange problem with ASP.NET MVC web application. IIS 7.5 throws back error 401 instead of 500 when application error occurs. This happens in production environment only, dev or staging works fine; the difficulty here is that I don't have access to the production environment so I have to replicate issue on my own to see what is wrong.

Any suggestions?

Answer 1

401 means that Authorisation is required.. Do you use custom error pages? and if so does your application have access to the custom error pages? that would be my first guess.