OK. So I did this. When I go through the install, it reboots, but there is no Firewire icon or external drive when the G5 restarts for installation.

Do I have to have file sharing on? Do I have to configure the Firewire ports for use like I did for the Ethernet port?

So either one of the Firewire 400 ports is bad or the cable is bad. Is there any way to hardware test the firewire ports?