When using a firewire interface (Digi002, 003, MBox2Pro) with ProTools on a MacPro and other newer Macintosh models, normal operation can be interrupted by the Network system preference option to use firewire as a network port. To stop this, follow these steps.

For Mac OS 10.4 Tiger:
1) Quit Pro Tools and all other applications.
2) Click the Apple menu and choose System Preferences.
3) Select NETWORK
4) Set the button next to "Show" to display "Built-in Firewire."
5) Next to "Configure IPv4" change the option from
"Using DHCP"
to
"OFF"
6) Click "Apply Now" at the bottom of the window and quit System Preferences.
7) Relaunch ProTools

For Mac OS 10.5 Leopard:
1) Quit Pro Tools and all other applications.
2) Click the Apple menu and choose System Preferences.
3) Select NETWORK
4) The left side of this window will list network ports. Single-click "Firewire"
5) Next to "Configure" change the option from
"Using DHCP"
to
"OFF"
6) Click "Apply" at the bottom of the window and quit System Preferences.
7) Relaunch ProTools