Webcam does not work.?

OK so here is the problem. I use a xbox cam on my computer and has always worked. It stopped working for omegle and chat roulette and all things like that including skype. But it works for a video chat program called oovoo. I tried to reinstall the flash and whatnot and yet still does not work. I also tried to downgrade to a previous version still it does not work. Does anyone have any help on what the problem could be? any help is appreciated:)