Help! Macally 6-port PCI firewire card hangs G4 dual 450...

I just purchased the MacAlly PCI 6-port firewire card for my mac G4
dual 450. The onboard firewire ports died recently and I need access
to my multimedia firewire drives like yesterday.

Now, when I plug anything into one or more of the actual ports--even
just a cable with no drive attached--the computer seems to "hang"
during the initial driver load during startup. If I boot up with no
cables/drives attached, everything is cool. But if I try to attach a
drive while the computer is on, it freezes right then and there (well,
the mouse seems to work but I can't select or launch any apps).

Is this card not compatible with my computer? Here are the specs:

Power Mac dual 450 G4, 2 internal ATA drives, 1.37 gb of ram, Geforce
video card, Pro Tools Mix Plus system (1 PCI core card in slot 2, and
one "farm" PCI card in slot 3), and your 6-port firewire card in the
last slot (4). I'm running system 9.2.2.

Any ideas?? I'm really desperate to get this working as I have
clients waiting for me!

Thanks,

Tim