Well there are hundreds of new viruses every day.

And it doesn't sound like a virus that did that to your comp, it just sounds like your comp had a temporary brain fart.

For virus and malware detection adn removal I STRONGLY recommend you download and use these programs on a weekly basis!!

-- Microsoft AntiSpyware
-- AdAware
-- Spybot Search&Destroy
-- AVG AntiVirus FREE Edition
-- PeerGuardian (methlabs.org)

I have all programs and run them at least once a week (actually most I have on a schedule so some run daily / every other day automatically) and I have NEVER had ANY problems with spyware, malware, or viruses since!