I am using it in firewire mode I'm afraid. It has both USB and Firewire connections but I always use it with firewire on the Macs. It's not really a big issue for me personally, the one occasion I couldn't boot my powerbook I simply booted it off my other mac! I just thought you'd appreciate the information. There's a chance I did something wrong, but I followed the instructions by the letter and triple-checked the results!
G

I think I was able to reproduce the problem. It seems that when there are two HFS+ partitions and the MBR has been created, the OS X installer only recognizes the first one as a bootable partition. It's nothing new in Tiger--just something I failed to notice earlier. I'm still not sure why greigd had this problem with both HFS+ partitions.

Even though the installer says the second partition isn't bootable, I was able to clone a working system to it using the restore tab in Disk Utility. I also noticed that Disk Utility won't erase this second HFS+ partition. I'm not sure what the issue is but I'd recommend just one HFS+ partition to be safe.