April 2013: More blue screens
This time, MS13-036/KB 2823324 -- a Black Tuesday security patch designed to replace a kernel-mode driver -- triggered all sorts of bogus warnings, and frequently froze machines. Primary suspects include a common IE add-in from Brazil, and Kaspersky Antivirus.
Microsoft pulled the patch, then issued a replacement patch: "Microsoft has released security update 2840149. This security update resolves the issue that was introduced by security update 2823324."