My Presonus Firebox isn't being recognized by my Mac Book Pro, but it works with other computers.
FireBox's AC Power Adapter needs to be plugged in during startup. Once the computer has booted, it can be removed.
"Due to a circuit design change, Mac Book Pro laptop computers will not supply sufficient power over the FireWire bus to initially boot up the FireBox. Once the FireBox has beeen initially powered on with the included external power supply, you may disconnect the external power supply, the FireBox can then be bus-powered."
Source: Firebox Tech Specs Page www.presonus.com