I have a mid-2009 MacBook Pro 2.53ghz Core 2 Due with 8 Gigs of ram running Mountain Lion.
I am attempting to upgrade the hard drive due to running out of space. I picked up a Seagate Momentus 750gb 7200rpm drive. This is not the hybrid XT drive that seems to cause problems for everybody.
I installed the new drive, put the old one in a usb enclosure and booted from it. I then attempted to use Carbon Copy Cloner to clone to the new internal drive. After cloning a few gigs though, the internal drive would disappear. I finally reinstalled the old drive and put the new one in the enclose and was able to clone that way. I reinstalled the new drive and the computer booted up fine, but would randomly freeze after a few minutes necessitating a hard shut down. I pulled out the new drive, put it in the enclosure and booted from it. The computer ran fine this way and I used it all day via USB with no problems. This lead me to believe the internal SATA cable was faulty as the drive worked fine externally but not internally.
I replaced the SATA cable today and thought the problem was fixed. The computer booted fine and ran for an hour. I used disk utility to verify the drive and repair permissions, but then the computer froze again. I restarted and it ran fine for a few minutes than froze. After each restart the computer will run for a while and then freeze. Any ideas way the drIve boots and works fine externally but not internally? The old drive works perfectly fine internally as well. I don't see a problem with the new drive since it works great externally when I boot from it.