Good news. I have connected the Eventide H8000FW to my macintosh laptop and the firewire is locking. This at least rules out a hardware issue with the Eventide.
So, I have tried 3 cables, 3 firewire cards/busses, and 2 computers. The only thing that is a factor now is the driver on Windows XP, which I have reinstalled.
I've bought an external back-up drive to make a clone of the entire system prior to further tests.
