I just transferred over 200GB of back-up photos to an old Seagate USB drive. The transfer went through (took two hours) and the files showed up on the drive. But once I tried to open a single photo my MBP Retina (10.9) froze up. After restarting the computer the drive no longer shows up and I get a "The disk you inserted was not readable by this computer." I tried the drive on my Mac Pro tower (10.8) with the same result. I need help. Thanks!