I have this same exact WD External Hard Drive: http://www.amazon.com/Passport-Essential-Portable-External-Drive/dp/B0041OSQ9S I'm running the latest Mountain Lion on a 15" rMBPro and this drive is partitioned into two partitions. Both formatted in Mac OS Extended... I think. I did this so long ago, I can't remember. It's the one that allows me to boot from it should my MacBook HDD fail (one partition is a back-up/Carbon Copy). I've been using it perfectly fine up until about an hour ago where when I was trying to write 3 large files, totaling 1.5 GB to the drive, I noticed the write was taking abnormally long, and then the hard drive just disconnected itself, but the drives were still running when I felt it. Mac OSX then gave me the notification that "The disk was not ejected properly. If possible, always eject a disk before unplugging it or turning it off." Even though I did not eject it myself. So I plug it back in and it works, it's recognized by the computer and all, but it's taking forever to load the drive when I open it in Finder. It finally loads, and I can open a video I have on there no problem, but when I try to create a folder, it's taking abnormally long and giving me issues when it comes to saving the new folder's name. So then I try to rewrite the files again, the same thing happens as before. To make sure it's not my computer, I pull out my old 2010 13" MBPro, and I boot it up, plug it, experiencing the same issues. So back to my 15" rMBPro, I did a Verify Disk and a Repair Disk using Disk Utility, and they found nothing to be wrong with my disks. I unplug it, then plug it back in, and it works as before, but I still can't write the files. So I unplug it for a while, and restart my computer, and now when I plug it in it's recognized, but when I try to open up the drive in Finder, it won't let me. Finder hangs, then I get the "drive not ejected properly" error. If I plug it in and leave it for a minute, it just ejects itself (but leaves the disks spinning). I did this one more time, and the same thing is happening. Now I'm at a point where I can't even open the drive to let's say salvage my files on there and move them to a different one. It's not making any beeping noises, or weird sounds, but earlier while it was plugged in, it made two random beeps out of nowhere, and that was it. But it did beep randomly (like maybe one beep a week) at times. Nothing that would signify it failing however. It was also stationary when these problems started happening, so it's not like I moved it while the disks were spinning. Does anyone have any advice as to what may be going on, or what the problem is? I fear that I've lost all my files.