Hey could someone help me with this? Over the past week or so, when I wake my iMac up from sleeping (build 12E55, running OS 10.8.4) the screen comes on always, but it does not respond to my mouse (don't see the mouse anywhere, actually). I can still adjust screen brightness and volume with my keyboard, but the symbols for those don't even come up on the screen. I've never had a problem like this and hope I can get it fixed soon. Any help is appreciated!