Im running mountain lion, With all updates on a 2007 iMac c2d with 2gb's ram. My hard drive inventory is as follows - MAC OS Time machine ( Seagate 320gb ext ) Media 1 ( WD Elements 1tb ext ) Media 2 ( WD Elements 1tb ext ) Life studio ( Hitachi 500gb ext ) Media 2 is the issue. One moment its there, then I get the message about not ejecting correctly ( I haven't ejected the drive ) I reboot with the drives unplugged, Then replug them in and its there again for a moment. All of my ext drives are connected to two powered usb hubs. ( So theyre drawing power from the wall and not my mac ) If anyone has any ideas I'ld love to hear them please as this is infuriating me no end lol!