I have an interesting problem that has occurred on my mid 2012 MacBook Pro. I created on a 500 GB Samsung SSD a Windows partition for Win 7 Ultimate, and upgraded the setting on the NVIDIA video used on the Windows side. And after setting up and playing games in Win 7 I attempted to get back into MacOS when I noted that the Mac side wouldn't come up. I shut down completely and attempted to get into MacOS again, and again the Mac although made the Apple sound, I had no video. When I allowed the Mac to go into the WIndows side, it did load. I repeated the shut down and restart allowing the Mac to cool down, still no video on the Mac side. I have ordered a new logic board for it. I wanted to know if anyone else has seen this problem.