Mysterious Faulty Cable from Beyond
The original hard drive in the laptop was failing. Given the current prices of solid state disks, I purchased a Samsung EVO 840 250GB drive.
At first, everything went smoothly. However, three weeks after the install, the main partition's index files were lost! I decided to do a system restore using Time Machine. But I was unable to erase, partition, or write to the drive. I continued to get "unable to write to drive" and "bad last block" errors.
Finally, I tested the drive in another system and everything worked. Obviously, something was wrong with the laptop. After various tests and even the Apple Hard Diagnostic, I zeroed in on the issue being a faulty drive cable.
The repair went swimmingly! Install is fairly straight forward and simple, requiring only a micro philips screw driver. The repair guides here do a fantastic job of the steps needed. Basically, remove the bottom cover, unscrew the drive mounting brackets, unscrew the two ground screws, and it's out.
The ribbon can be a bit fragile, so it pays to handle it with care!
How did the original cable go bad? It was only touched once when the new drive was put in... and it worked for three weeks! Who knows? I've been repairing computers for over 10 years now and it seems cables can spontaneously fail. So, just because you've never touched the ribbon doesn't mean it can't fail!
Also, I'd advise getting the ribbon with the drive bracket already installed. You can certainly use the old one, but at a $10 difference, it's worth the hassle free install.
Getting the ribbon without the bracket isn't too bad, though. It merely adds a level of difficulty to the procedure as you must now remount the IR sensor to your old bracket. It's held on with a sticky film that doesn't transfer well.