So, I posted this question a few days ago:

Impact of increasing the MaxTokenSize for Kerberos Tickets

Since then the thought was to test our settings on two member servers, one with IIS and one without. I setup two GPOs to configure the MaxTokenSize reg setting to 48000 and MaxFieldLength/MaxRequestBytes to 64200 (based on MS KB2020943, these are set at 4/3 * T + 200). The member server seemed to work ok (a devalued tape backup server). The IIS server however has had some strange repercussions.

The IIS Sserver host Quest Software Archive Manager (AM) 4.5 that communicates with SQL Server 2005 Enterprise on Server 2003 R2. After the changes all looked good until the SQL Server hit 100% CPU.

I have removed the GPOS, removed the reg values and even replaced them with defaults (12000 for token size and can't remember the other one but was in a blog post about the issue in my other post). No change. Bouncing the IIS Server stops the high CPU and a colleague has looked at the SQL server and it is definitely the AM connection taking up the time/work on the SQL server.

I haven't changed the reg values on the SQL server or the DCs but am reluctant to do so without understanding why this has happened. I am guessing its to do with the overriding auth and group issue we have but I am not seeing Kerberos errors in either event log.

Has anyone seen something similar or does anyone have some tips? Was definitely blindsided by the Kerberos issue and am swimming against the tide to keep things functioning.