I just updated my MacBook Pro to Yosemite. I play a video game on full screen mode in Firefox, and like to take screen shots (shift+apple+3) sometimes while playing. It worked fine before, but now whenever I screenshot in full screen mode, all I get is a 26KB image that's entirely black. It will capture when I'm not in full screen, but why is it doing this now when I'm in full screen? How can I fix this?