I have been having lots of sleep and screen saver problems. When it would wake from sleep it would either crash, or lock up every app. When I started a screen saver it would get stuck in the screen saver when you typed your password, and the picture based screen savers were slow and choppy on external displays. This has been driving me crazy. I figured the best course of action was the do a clean re-install, since this computer was restored and upgraded from another computer that was upgraded also...so technically I haven't done a clean install since Snow Leopard. I went into recovery and actually wiped the Macintosh HD, installed ML and then used migration assistant to get everything back. No more problems! Yay! So if anyone else is having similar problems that worked for me.