I'm new to MOTU.

I have Win 7 64 bit and installed the latest drivers from MOTU.
When I turn on the device, Windows does not detect anything on the end of the firewire cable. My first reaction was: it must be a driver problem. But the killer is: even if the drivers are not installed or there is a driver problem, Windows should still *detect* an unknown device is present on the firewire bus.
Tests:
- I've uninstalled and reinstalled the drivers. Same deal.
I've tested on XP and the same deal.
I've tested on a friend's Win 7 PC, and the same deal.
I have tested all 3 PCs with a video camera firewire device, and all 3 detect an unknown device as soon as it is plugged in WITHOUT the drivers installed.
I have replaced the 6-to-6 pin firewire cable. Same result.
I have tested both ports on the device. Same result.
I've looked at the firewire hosts under device manager - it shows the firewire controller, but no connected device (known or unknown).
Either I've bought two faulty cables in a row, or the device is broken.
Can anyone fault my reasoning?
The guy I bought it off is a nice chap - he says it works with his Mac and he's willing to have a look at it in a day. But I just can't see how a Mac will make a physical FWire connection when a PC can't ... unless the cables are broken.
Thanks in advance for all suggestions.
Entilza.