I recently reached capacity on a My Passport 1.0 Tb drive used for storing movies. I bought another My Passport (same model and capacity) and transferred roughly half the movies to the new disk. This worked well until I rebooted the computer. Now it no longer recognises the second disk. I went back to the store where I bought the disk and plugged it into a Mac Book and it was recognised immediately. It also worked on my machine when I got home until I rebooted the computer again.
I have the disks hooked up to a Mac Mini (second latest edition) using the Lion OS. I have tried disk utilities and different cables, USB ports, etc., all to no avail.
Any help would be very much appreciated.