Does the disk show up in Disk Utility? If the device is working right and the hard drive is just corrupted you should see the disk in Disk Utility but the volume will be grayed out if it isn't mounted. You can click the mount button and it will try to mount it, or you can run First AID on the disk.
If it doesn't show up in Disk Utility, does it show up in system profiler under USB/Firewire devices?
Of course they have changed Disk Utility a little in Tiger, I can't remember all the options Panther had.
I just did this with an iPod this morning.
Oh also, if the device isn't showing up in system profiler there is probably something wrong with the external hard drive enclosure. You can (if you feel comfortable) probably get the actually hard drive out from inside the case and put it into your Mac.