Windows Server 2008 R2 Security Patches Break SharePoint 2010 User Authentication

Today I had to restore user authentication on a SharePoint farm. The farm had been functional yesterday, but upon arriving into work this morning users would get a low-level error message when trying to log in.

Microsoft pushed out some security patches yesterday for Windows Server 2008 R2. A discussion of some of the problems encountered by users can be found here.

I found that on this farm, the Forefront Identity Manager Synchronization Service failed to start, which in turn broke the User Synchronization Service, which then broke user authentication.

I removed the following updates to restore user authentication:

KB2769369

KB2757638

KB2756920

KB2742598

KB2736418

Uninstalling all five of these updates may be more than is necessary, but will fix the problem.

This farm's application server did not have Windows Server 2008 R2 Service Pack 1 installed, so that may be a precondition of these errors occurring.

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