They're not the only AV company to make a HUGE **** up with the signature defs - I use computer associates and a few months back they decided that a load of service pack 3 windows files were a virus and quarantined them, causing the PC to go into safe recovery mode where it says files have been modifed and asks for the windows disc to replace them.
That wouldn't be so bad IF it wasn't asking for my service pack 3 disc which didn't exist at that point as I'd installed on SP2 and upgraded to SP3 - DUH!
It took them well over 24 hours with their forums lit up blue like a christmas tree with pissed off users......
Meanwhile their best advice was to "disable realtime scanning" - I kid you not!

- No fecking way am I gonna do that, luckily disabling the dumbass hueristics scanner cured it till the update was released.
They also decided a couple of keygens I've had for years were suddenly some new virus and only fixed it when I sent a sample in which first got me an automated reply saying it was malicious until someone with a brain checked the code out and cleared it as safe.
Ironicly that cured both keygens even though I only sent in one - They were both by the same cracker so I guess it was just something in his coding they didn't like!