I have an external 3TB HD plugged into my Mac Mini. Starting about a week ago the hard drive will display the contents of the folders as completely empty. I can open the hard drive, view the folder contents, but there are no files visible. I can unmount and remount the hard drive and at that point all of the files show up again. This issue reoccurs daily. I receive no errors, it just shows no files until I unplug/replug in the drive. Any ideas???