I've recently had my macbook pro crash on me while using it. It just happens randomly, even when just surfing the web or listening to music on itunes. The screen will suddenly transition to a solid light blue screen. I can hit keys like the volume up and down and hear the little blips, and itunes will even continue to run fine, it's just that the blue screen remains and I can't regain control of the computer until I manually shut it down. What might be wrong with my computer?