i have a late 2012 MacBook Pro with updated OS X Yosemite, i was using the laptop and everything froze. i restarted it. then when the laptop turned on a folder with a question mark displayed in stead of the apple logo. I tried reinstalling Yosemite(usb bootdisk) however when it asked to choose a hard drive the MacintoshHD was not displayed. I took the my hard drive out of my mac and put in an other mac, the hard rive booted up fine with no issues. I took the other macs hard drive and it also booted up fine. so the hard drive cable nor the hard drive are defective. after several time of unpluging the hard drive and plugin it back it it magically worked. i used the computer for 3 days and everything happened again the computer froze and once i restarted it the same log came up. HELP!!