Hello, I have a 15" MacBook Pro (Late 2011) which seems to have a problem that can not be solved. I have had 0 problems with my laptop during the years I have had it and now I am having a string of problems. The first of these problems began around 3 weeks ago. I was using my laptop for a few hours then It went suddenly to a completely blue screen with vertical lines. I would try booting into safe mode/hardware test/recovery mode with no avail. I have AppleCare so I proceeded to take my laptop to my local Apple repairer to see if they knew what the issue was. They never really told me what was wrong with it and proceeded to install a new logic board and screen. (I also upgraded my RAM to 8gb while I was there). I used the computer for about a week and bam! My computer this time went to a grey screen then nothing. I restarted my computer by holding down the power button and waited. Now I cannot get past the loading screen (Apple logo circle spinning thingo). Again I cannot boot into safe mode/recovery/hardware test. Again I take my computer to my repairer. I tell them the issue and they proceed in replacing my HDD, saying that it was "on its last legs". They also installed a clean install of Mountain Lion. Thinking my issue has been solved I downloaded programs I needed ect. And now today, 2 days after I have been using my laptop I am having exactly the same issue. Using laptop normally, then agian black screen. Try restarting/hardware test ect and again I cannot boot past the loading screen. Please help me before I throw this laptop out my window.