I have an iMac and an external 27" monitor sitting beside each other on my desk. I would like to have the ability to watch a movie on the external while also having the ability to work on my iMac. However, anytime I put a movie into fullscreen in VLC or QT the other screen that the movie is not on also goes black and unusable. Does anyone have a solution to this issue? I'm using Mountain Lion if that makes any difference.