KB974571 Breaks OCS 2007 R2

I came back from vacation to find that I was unable to login to OCS. Turns out that an update installed on 10/14 broke the front-end services for OCS. The event log shows the following error:

The evaluation period for Microsoft Office Communications Server 2007 R2  has expired. Please upgrade from the evaluation version to the full released version of the product.

Uninstalling the KB974581 update corrected the problem.

Big thanks to Dietmar Kraume’s blog post at http://tinyurl.com/yjefeg9 for pointing to the solution.