Hello,
Have you installed any other applications during this period or updated any drivers(particularly any new video or audio drivers)? If you’ve tried a *complete* uninstall of After FX (including any preferences) and you still get the same problem, perhaps it is related to another software conflict?
It might also be worth starting the application with the caps-lock key turned on and see if it crashes only once you release it.
let me know how you get on!
chris