I occasionally have the same problem on my laptop (ASUS G74Sx) running Windows 7.
Ive only seems to happen when i play mass effect 1 or 2 (in fact it didnt start happening untill after i installed mass effect 1 in mid february.) Ive also gotten other keyboard glitches such as it constantly typing 3 even if i am not pressing any buttons. Restarting tends to stop it from glitching for me but the problems tend to reappear.
I think the problem is software not hardware becasue my keyboard buttons do not behave weird in a mechanical way. im going to try to reinstall or rollback my keyboard driver and see if that will work but im not sure it will fix the problem.
If anyone else has an other ideas of the problem or a solution please help us.