The video camera built in to my Mac laptop seems to have stopped working. When I bring up Photo Booth, for example, it just shows a video camera icon crossed out. Similarly for other applications. Is there any way to tell if it's physically broken or if it's some setting in System Preferences or something?
I recommend trying the instructions mentioned on the Apple Support site first.
Do you have the AC Adapter connected?
If you do, here's a site that may help.