Help! mobile hard drvie problem with Powerbook

I've just bought myself a LaCie (Porsche) mobile hard drive (80gb USB version). The problem is that it doesnt seem to want to mount on my powerbook. Ive tried it with my dell desktop, my sony laptop and my imac and it works fine, but it wont seem to mount on any of the powerbooks I have here (all 15 inch Alu ones). I reckon that for some reason its not drawing enough power from the USB port(s) (I've tried it both with a single cable attached and with the additional power sharing cable that you get in the box, neither method worked. But if I put a powered USB hub between the powerbook and the drive it works fine. Obviously this isnt much good on the road. Anyone got any ideas for a work-around or am I gonna have to send this sucker back .