The above thread put me on the right path, and I hope my experience helps others.
Problem: iMac suddently stopped showing two 2TB iomega hard drives that store our videos, photos, etc. (reformatting was not an option...) I tried different USB ports, firewire, restarting, connecting to my MacBook, etc. and message always said drives cannot be read by either iMac or MacBook. It seemed too coindicental for 2 drives to have failed at once...
Solution:
1) Based on above thread, I went to System Profile in my MacBook with one drive connected via USB. The drive was seen there.
2) Next, I went to Disk Utility, where the drive was seen. Icon showd up as "2TB External..." and underneath and indented there was a gray name that was NOT the name I had given the drive.
3) I hit "Verified Disk" -- and it said "Invalid Index Key. ...(drive name I HAD given drive)...found corrupt and needs to be repaired. Error... Click Repair Disk."
4) I clicked "Repair Disk" a first time. It failed with message "Disk Utility Stopped Repairing..." -- not sure why.
5) I tried "Repari Disk" again, and this time it took longer, gave many more lines in the window as it did it's job, had messages in green instead of red, and the file was repaired!
6) Disconnected drive, turned off MacBook and drive, rebooted MacBook, connected drive via USB, turned on drive -- and there it was on the desktop with its correct assigned name!
I hope this helps.