Thought this may be of interest to people as since setting up doing IT support and one of my first customers brought a Mid-2012 MacBook Pro to me which was failing to detect the hard drive. This was traced down to a faulty cable and from looking online seemed to be a pretty common issue, so I replaced the cable and all was well again, but last week it failed again so rather than simply tell them it may keep needing new cables I decided it warranted some further investigation in to the cause. Basically the inside of the chassis has machining marks and is not smooth like the outside, so the cable appears to chaff against it exposing the traces and then short against the chassis, causing problems. Came up with a very cheap fix for the problem in the video below which sorted it out and didn't even require a second replacement cable. http://youtu.be/Amg5w0rlwDo I hope this helps a few people out - it seems ridiculous this problem existed for several generations of MacBook Pro and the only previous fix seemed to be to keep shoving new $40 cables in it each time! I can't guarantee this will fix the problem for everyone, but personally I'll be carrying it out on every MacBook Pro which passes across my workbench as preventative maintenance!