ghost typing

It seems that when I select a dialog box to type something in, the computer starts typing a bunch of "2's" without me even touching the keyboard. It was happening earlier in the day but the computer only typed 2 or 3 "2's" and I simply thought it was a problem with the keyboard and I would fix it later. But when it got really bad and I unplugged my keyboard it continued. I thought that maybe I had gotten hacked so I unplugged my internet and still the "2's" keep coming. I am really hoping this is an OS coding glitch or something like that because getting hacked defeats one of the greatest perks to owning a Mac

(I own an Aluminum iMac 20" (bought in 2007)

the only thing i was going to suggest is giving the '2' key a blast with some compressed air but if you have unplugged the keyboard....