I have a 2012 15-inch MacBook Pro (non-retina). I am running OS X 10.8.2. Every time the computer goes to sleep, it locks up and I can't revive it. In addition, when I reboot the computer, it stays at the grey screen with no Apple logo. In order to get past the grey screen I have to reset the PRAM.
I checked the hard drive using the Disk Utility and it says the hard drive is okay. What could be the problem?