In newer computers running Mac OS 10.5, try disabling the firewire option in the Network section of System Preferences.
1) From the Apple menu, choose System Preferences
2) In the third row, choose NETWORK.
3) The Network panel will list available ports on the left, including FIREWIRE. Single-click FIREWIRE to select it.
4) The main network window will show Firewire network status. Where you see “Configure : Using DHCP,” Change the status to “OFF” instead of Using DHCP.
5) Quit System Preferences.