This is interesting - I have a high-end Sony Vid Cam and it isn't working with iMovie/Final Cut. I've searched allover Apple Discussions and the best I can find is that *some* models of Macs have tempramental USB/Firewire ports. But I don't buy that because everything else works fine for me.
I've tried lots of things - new cables, different macs, different settings on the Camera - which leaves me to believe it is the camera. But I know of other people with the same camera that use it. There's no reason to suspect the thing is broken.
On my G5 there is a funny almost cube like fire-wire cable. I've never seen anything like it before, do you using a firewire cable shaped like this will solve anything.