isight not working on intelBased iMac core 2 duo osx 10.8.2

in photobooth, facetime and skype... i got the green light to come on... but no camera is visasble in any application... this is my `1st mac and decided to try one out as im a PC type person.... it does show up in USB system profiler so it sees it there but just no image from the camera ... ive tried the resetting PVram, command P r restart, tolding the power button for 10 secs etc... everything i saw in the apple formus and to no avail ... HELP?