I seem to have a similar problem and looking for help. The computer swears firewire is fine, but it never sees my camera.

 Vista Home Premium 32

Intel q6600, ASUS P5KC (Intel 38 chiipset)

Sony FX7 camcorder

Everything used to work fineb with all of this hardware. I recently got Studio 14 and wanted to try out some of the new stuff. 

I set up to import from the camcorder and- nothing.  The Camcorder shows iLink, but Windows sees nothing.

Yes, the camera is on and in VCR mode.

Tried a new cable, though the old one tested good with a multimeter.

Firewire pot shows in device manager as ok. Tried disable/enable, uninstall - reinstall, and selecting other drivers to install 

Tried the 1394 on front and back (both worked before)

I have only 1 firewire device and only this computer with firewire.

Google solutions are proving to be useless (Vista doesn't support firewire?  Really?  bah - urban legend nonsense)

As the instigator of this thread (last June) it's been interesting to read that others have had similar problems.

However, thanks to Marc my Firewire problem has been resolved.

His suggestion (why didn't I think of it?) was to fit a PCI to Firewire card.

Did this (cost < £10) and all's well and running very efficiently.

Seems that, after all, it was a hardware fault (? chip on motherboard) as has been suggested elsewhere.

Many thanks to all who contributed and particularly to Marc for his suggestion

Bazzer