OCS 2007 R2 - KB974571 Breaks Front End Servers!

Microsoft Security Update KB974571 (vulnerability in Windows CryptoAPI) has a known compatibility problem with OCS 2007 R2 that can bite you in two different ways:

1. New OCS installation - When you run the Deploy Server Wizard to install/configure your new Front End Server it will fail with error [0xC3EC796C].  If you read the deployment log there will be a server activation error related to the Deployment Wizard failing to read OCS version information and a message that this could be caused by the computer clock not being set to the correct date and time; in reality the problem has nothing to do with with computer date or time.
2. Existing OCS installation - If you install KB974571 on an existing OCS 2007 R2 Front End server the OCS Front End service will stop with error [0xC3E93C23].  Restarting the server will not restart the service and the service cannot be restarted manually.

In both cases the fix is to simply uninstall the update (KB974571) and then restart your server.  After the restart you'll be able to complete the Deployment Wizard and/or restart the OCS Front End service.