Keep tapping the F8 key on your keyboard when your computer starts.
If you can choose SAFE MODE and run a virus scan.
Do you have Anti protection? click here and install this from safe mode. You cnnot access the internet from safe mode so you cannot update it (as i'm aware). I do not use AVG myself so if you need help with ask and i'm sure someone will help.
This may pick up a virus. Using Kazza it sounds like you have a virus.
It may also be a coincidence and the keyboard is faulty.