Q: Macbook Air built-in camera stopped working after installing Mavericks OS

Tried all the suggections that were posted here by some but to no avail. can't use my camera on Facetime, Photobooth, Skype, Yahoo Messenger, Google Talk, etc. "No Camera Detected" or just the black thing on Facetime . The green light beside the camera lights up but no picture. black, blank screen. once i talked to an Apple Genius but he wasn't able to fix the problem.