Hey Rob here again, I thought that I would share with you some of the things that we see where Internet Explorer Kerberos authentication fails.
It is important to understand the default behavior of Internet Explorer and its support for Kerberos authentication so that you don’t start ripping out your hair (can’t speak to what Ned does here). I have listed three very common problems that we typically see when Kerberos authentication is failing with web-based applications.
Source : Ask the Directory Services Team