A few nights ago while using it my screen shifted horizontally, as if the window got left-swiped (like on a phone or tablet) half way across the screen, with a black line down the middle. i lost all functionality at that point so i did a hard shut down. upon my first attempt to reboot, i got the usual grey screen w/the apple but then the apple disappeared and the computer just froze on a blank gray screen, never making it to the point where i'd select which user. at this point i googled the problem and it was suggested to zap the PRAM. this did the trick, but withing two minutes my screen went dark-gray (almost black, but definitely lit) and blank. rebooted again and got the blank gray screen again. this time with my fans going 100mph. i shut it down and rebooted again. this time i got lucky and was able to log in. immediately ran disk utility repair disk as well as permissions. tests results said no problems were found. Two minutes later the screen went dark gray/black again, and now it won't get past the light gray screen whenever i try to start up? unit in question is 2011 15" model (w/dvd drive) with a (roughly) 2 year old SSD that's probably 25% full at best (if that even matters). Not sure if it's related but about two weeks leading up to this my dock (which i use the auto-hide function on) would not pop up upon startup until i clicked on my desk top at least 3 times, otherwise it wouldn't respond when i slid the mouse curse over to it. could bad RAM cause this or do i have a bigger problem? FWIW i also disconnected all peripherals to no avail.