Sorry, Let me clarify. I meant a tethered power solution that is reliable. Because some macbooks have limited firewire power, there can be insufficient power to the back.
It isn't actually a limited power issue. There is nothing wrong with the power output per se from any of the Macbooks. Ie There is enough watts to power the camera.
The issue is that part of the signal that maintains the firewire connection can suddenly drop, thus breaking the connection. We have been looking into this into a lot of detail along with Apple - so it's good we have their attention.
Suffice to say it doesn't seem to affect all users so it is a strange 'feature' of the Macs.
To cure it until Apple come up with a solution then use a FireWire repeaters or something like the Lindy FW800 cable with a built in repeater. As these contain additional firewire circuits it seems to prevent the signal drop.