There's a brand new virus that's just appeared that only effects blackberrys, specifically the 7290. It spreads by email. It causes your handheld to freeze randomly, and when the keyboard lock is turned on (such as when you put the device into a case), prevents you from unlocking the device if you use a password. The only known workaround that prevents the complete wiping of the device after too many incorrect password attemps is to contact UPS and ship your blackberry to BlackBerryForums user CK99a...
sorry, couldn't resist
(thanks to Soupy Sales for this one