McAffee is having a bit of trouble with their latest software update according to this article on Engadget
We’re hearing from all over that a bad McAfee for Windows XP update is causing computers worldwide to shut down. Apparently DAT update 5958 deletes the svchost.exe file, which then triggers a false-positive in McAfee itself and sets off a chain of uncontrolled restarts and loss of networking functionality. Yeah, wild — Twitter is basically going nuts, and McAfee’s support site appears to be down. There are some fixes floating around out there, but it may be too late — the final tally of borked PCs today may reach into the millions. We’ve already heard anecdotally that an Intel facility has been affected, as well as Dish Network call centers, and we’re sure there are going to be more reports as the day wears on.
Wow. Talk about epic fail.