I have a problem with my Samsung 830 SSD that I have used it with my 2012 MacBook Pro 13 since it was new. It has worked fine until recently when the computer suddenly froze up. I turned off the computer, but when I started it up again it would not boot and showed the stop sign screen. I should perhaps mention that I recently before the crash had installed a Yosemite update. I have never tried to enable TRIM on the drive. I was able to access the SSD via USB when I installed a old hard drive into the computer. I ran Disk Utility on the SSD and it said it couldnt repair it, so I backed up some files and reformatted it. I then tried to install Yosemite via a bootable USB-stick with the SSD in the computer, but it threw me a error (File system verify or repair failed). I wiped the SSD again and tried to install Yosemite on it with it connected via USB, which worked fine. But when I installed it in the computer and booted it up it only showed the stop sign screen again. I tried again to boot it up connected visa USB, and it worked fine. I also tried to reset the SSD from a Time Machine backup, which seem to work fine, but it still wont boot inside of the computer. Conclusions: Nothing seems to be wrong with the mother board, hard drive connector, etc since I have no problems when I install another hard drive in the computer. Nothing seems to be wrong with the SSD, since I'm able to access it via USB and read and write files to it I can boot into OS X (both from a fresh install and from a Time Machine backup) from the drive when its connected via USB but not when its installed inside of the computer. Has anybody any clue what might be the problem?