Spotted on El Reg at lunchtime:
McAfee false-positive glitch fells PCs worldwide ? The Register
It _appears_ to just affect machines on mcafee engine 5100 (we're on 53** here) and testing on a spare XP vm* does cause issues if you're on 5100 and use the aforementioned dat file. Nothing happens on 5200 or 5300 when I tested, but I disclaim all responsibilty for anyone acting on the info :).
*snapshots are awesome.