I have a 120GB disc in a USB/firewire enclosure.
I used it, connecting via USB 2.0, as a backup disc for my desktop. No problems for a year or so.
Recently I bought a new laptop as a desktop replacement and started using the same disc and enclosure, but connected to the laptop's firewire port. The disk functioned as expected.
Within a couple of days the disc became inaccessible: showed as unformatted. Went into disc management, tried changing the drive letter and generally fiddled about with no luck. Couldn't recover anything with Acronis Disk Director.
This happened 3 or 4 times in the space of a few days, whether formatted in NTFS or FAT32.
I reformatted again, connected to the laptop via USB, and have had a couple of months with no problems.
Any ideas please?