It was working fine last week. I was watching Netflix when it started freezing. I would restart but then it stopped booting at all. It shows the Apple logo properly, and then when it seems like it will finish booting it just shows a gray/whiteish screen. It doesn't seem to be frozen, capslocking still shows LED. I tried only using one RAM memory at a time, same result. I tried booting up with a USB installation setup, I can pick my USB when I turn on the computer pressing option key. It does the same, gray screen after apple logo. I did PRAM reset, fsck, etc. I was hoping it was the hard drive. I disconnected it but the bootable USB still behaves the same way. Could it be the graphics card? I was googling but I was only able to find about overheating cards showing horizontal lines, etc but not my symptoms. Any help will be greatly appreciated!