Can't boot from firewire disk

[angusmillar]

I just bought a Seagate external firewire drive and was really annoyed when I discovered couldn't boot from it after cloning my drive to it (I'm using 12" powerbook)
Same as you drive appears as an option in Startup disk system preference but if selected still boots off internal, also doesn't appear as option if I boot with option key. I found this while surfing though, I'm going to try but means recloning about 300GB, not going to happen soon but maybe you may feel like giving a go. Apologies to originator of this info, I just can't remember where I got it.

In the past I have had the symptoms you describe when I have formatted an external drive with disk utility and cloned to it, and not been able to boot. The cause was that for a while (not sure about now) when Disk Utility formatted an external drive it left the "ignore ownership" box in the "Get Info" window ticked. In this situation the clone will happen OK (and it will appear as a bootable option) but not boot. It is no good unticking after the clone. It has to be unticked before the clone.

It may be worth your checking what the "ignore ownership" box says on your Seagate.