Hey guys I have this same exact problem. It happens the first time I switch to camera mode in iMovie. If I restart and try it again, it doesn't reoccur. The computer needs to be turned off completely and then back on for the problem to reoccur. I called Apple and they tried to help me over the phone and decided I would need to send the computer to them for repair. Well guess what I did and got the computer back and they never fixed it! That made me pretty mad. If I take the computer into one of the Apple stores and show this problem to them, do you think they'll fix it? It's still under warranty so it shouldn't be a problem...