Not so helpful after the event, but when it comes to external hard drives for Macs, always go with firewire over USB. Not only is it faster, but its considerably more stable and reliable. Much as I hate to say it, USB HDs are much better supported on PCs. Macs are better at USB2 drives these days, but USB 1.1 is something you should really steer clear of on Mac. Even when they work right, they are dog slow. Try an iPod, and you'll see. Don't know why iPods seem to work better, I guess the controller chips have better drivers.
Could you pick up a cheap firewire case for it? You should make a few bucks back if you eBay the USB one.