I have a new-ish 2+ year old iMac, (the first of the new slim models). With that I have the standard issue wireless keyboard and 'magic' mouse.....
Every once in a while something, I'm guessing the keyboard, throws a wobbler. Typing anything anywhere just finds additional letters being added in 1's and 2;s. In the case of yesterdays bout, I,T, and U.
Switched off and on, checked obvious things, to no avail. As before, leaving it switched off all night seems to resolve it, and I'm guessing it'll be OK for a few months now.
Any ideas, duff keyboard maybe ?