The QC9K uses digital zoom, right? Regardless this sounds like a software problem, and software doesn't really wear out, per se. This should be fixable, but figuring out what the specific issue is could be tricky.

If I were going to take a blind stab at it, I'd say check again and make sure face tracking isn't on in the camera settings.  If you're sure it's off, try leaving the camera configuration dialog open while you do some things (wave your hand in front of the camera) to see if it still has the problem. I've had webcam drivers that would revert to their default settings as soon as I closed the configuration panel, but they did it from the moment I installed them, so I'm doubtful this is the solution. If it was working correctly before, something must have changed recently within your system to cause the problem. I'm still leaning toward something within the camera settings more than an external problem.

EDIT: One last thought- have you tried rolling back to an earlier version of the camera driver/software?

Try to reset the camera or software(if possible).