December 2010: Patch brings down Task Scheduler
MS10-092 was a rather innocuous patch, designed to plug a hole in Windows Task Scheduler.
But shortly after people started installing it, they saw messages saying, "The task image is corrupt or has been tampered with." In some cases, the task was killed. In other cases, the machine froze. Simply uninstalling the patch didn't solve the problem -- great prelude to the holiday season.
KB 2305420 has pages and pages of manual workarounds.