Cannot format external harddrive

I have a Seagate 1.5 TB external. I can no longer read data from it. I want to erase all data and reformat.

Conventional Efforts:
When I plug it in to my MBP (via Firewire 800), it shows up on the desktop as mounted. However, when I try to access the files on it via Finder, Finder crashes (beachball). I open disk utility, and I can see the disk. When I press erase, the dialog is stuck at "Unmounting Disk".

Why does this happen?

Sounds like the disk has gone south

But first try a disk repair in Disk Utility

Ya, I figured as much. Any operation in DiskUtility leads it to hang. I "fixed" everything by erasing the disk through diskutil then repartitioning it.