Adaptec DV issues

I have recently installed an Adaptec OHCI compliant FireWire card into an
older PIII PC. System completely freezes after several seconds of operation.
The Tyan mobo has 1 PIII uP (600E) and my drives are 2X4Gb SCSI controlled
by an Adaptec2940UW card. W2K SP4 is on these drives. I have a 120Gb IDE
ATA100 drive for "capturing" the DV video. Have flashed mobo BIOS, SCSI
controller BIOS. Have downloaded most recent drivers for the nVidia TNT2 AGP
card, plus all other cards in the machine (IN5669 Modem, Vibra128 soundcard,
FA311 Netgear network card). I have tried another 1394 card (different
brand) with the same results. I have the most recent 4 in 1 drivers for the
VIA 133A chipset. I have removed all the cards except the AGP and the 1394
and the system works for longer but eventually crashes. I have tried many
BIOS setting, PCI latency, AGP aperture, ACPI On/Off with differing results.
I'm using the microsoft DV drivers rather than the TI drivers as Premiere
won't work with them. Have resigned myself to the fact that this DV card
will just not work in this configuration. When the DV card is removed the
system becomes stable. Anybody got any thoughts, thanks in advance.