(To see this exact same discussion but with the Log Files included, Click the link below)
Randomly, When I restart my rMBP or boot up the screen goes black after i put my password and press enter. This forces me to hard reset. It sometimes does not even stop unless you boot to Safe Mode and toggle with the graphics settings. I thought it was GfxCardStatus Conflicting with a driver but this does not happen to be the case. I still use GfxCardStatus and just to be on the safe side for now, I open it from my Documents Folder after each boot. This really stupid and embarrassing at times when you have friends over and want to show off your mac's power and performance like Start up times for example and you have to explain to them that there are some bugs in "The World's Most Advanced Operating System Ever" OS X Mountain Lion. I live around Apple Haters who stick to Windows till death; If they saw this it would just add more fuel to the fire that "Windows is better than Apple". I'm paying for Premium high quality products from Apple, not garbage. Now this is an insult to the software, not the hardware but if I wanted to get black screen and errors then I could have just stuck with Windows and I could get that for free in 5 minutes visiting low quality ***** websites. lol.
Lastly, I want to note that during one episode of my rMBP's ******* blackout moment, after I got out of Safe Mode, restarted the computer, and logged in; Error messages involving KeyChain Access popped up. Apparently App Store, iMessage, iCloud, Address Book, Mail, and all other applications that used your accounts information was unable to information fro KeyChain. I don't remember exactly but it something like this "024739-39-a70h-892hh Could Not Access KeyChain. Would you like to Reset to Default?" I clicked "Reset To Default" but the messages continued to pop up that KeyChain cannot be accessed. It wasn't until a few Google Searches later that I can go to Utilities>KeyChain Access and use the First Aid Feature to fix the corrupted KeyChain File.
If you go to Utilities>Console and Open the System Diagnostics Report, The Window Server Crashes I believe to be the Blame as it involves the CoreGraphics. I have posted 2 most recent crashes of this nature and one of Security Agent which I believe is KeyChain Access.
To see the Logs go to my detailed discussion. Same subject but with "(Detailed)" added on to the end of the subject.