Did you by chance disable the webcam on your account? The ALS is tied to the webcam, and so if you disable that, it will disable the automatic brightness adjusting. The keyboard backlighting I believe is also tied to the ALS, so it doesn't turn on when you're in a brightly lit area.
So I would start my efforts with the webcam. Maybe you installed skype or some other program and used it to disable the webcam for example.