ApplicationHost.config error with IIS7, Dot Net 1.1 and Windows Server 2008 Service Pack 2

We came across a very odd issue today where the following error message would be displayed within IIS.  The error message itself is not terribly helpful as usual, and there are no other error messages records in any event logs or log files.

This was happening whenever any of the configuration options in IIS7, on a site where the application pool was running Dot Net 1.1.   I immediately spent hours poring over applicationHost.config, as well as any web.config files and configuration files on the server.  Over a day later, after rebuilding the server and IIS7 multiple times I was starting to come to the conclusion that it might be something I had installed, so I ran up another server as a controlled test.

I did this in the following order :

1. Install Windows Server 2008 Web Edition off a media set that I knew was good.
2. I installed Windows Server 2008 Service Pack 2.
3. I installed any missing Hotfixes as determined by our WSUS Server.
4. I installed IIS using the Web Platform Installer
5. I installed Dot Net 1.1 and assorted Dot Net 1.1 Service Packs and hotfixes.
6. I opened IIS, set the default web site to the "ASP.NET 1.1" application pool.
7. I opened the Default Web Site configuration in IIS manager and attempted to view Handler Mappings.

At this stage the server was a vanilla install with no code on it and I was able to generate the same error as above, and the problem must be one of the above steps.  As we have other Dot Net 1.1 servers running Windows Server 2008 I quickly had a look at their configuration and only one thing stood out – none of them had Windows Server 2008 Service Pack 2.  I immediately uninstalled the Service Pack to see if it would have any effect.  Immediately I was able to browse and modify configuration settings in IIS7!  The question still remains as to what in the Service Pack was causing the problem.  Unfortunately we still have some clients who need to use Dot Net 1.1 and until a resolution or hotfix comes forth, we will not be using Service Pack 2 on any of those servers.

If you come across the error it will only manifest in these conditions and can be resolved quickly by a removal of Service Pack 2.

• IIS7
• Windows Server 2008 Service Pack 2 
• Dot Net 1.1 installed and application pool of Site set to use Dot Net 1.1
• Trying to view or modify configuration data for the Site

Hopefully this will help a few people to spend less time butting their head against a wall than I did.