I recently upgraded the ram in my mid 2012 MacBook Pro from 4 gb to 16 gb. Everything was fine for about two days until I switched tabs in chrome and the mouse just disappeared and never came back. I restarted and got the flashing question mark folder. After a few try's it booted but after a few minutes did the same thing. I tried putting resetting the pram but couldn't get the sound so I don't think that worked I also tried putting in the old ram and am still getting the flashing question mark every time I boot. Any help is appreciated. Thanks !