I'm using the firewire port on the back plate of the motherboard so it's not a connection problem and I already have the latest nForce drivers installed.
From looking through the ASUS forums apparently there are a lot of other people having this problem. Someone suggested installing 2 post-SP2 XP patches that are supposed to fix various firewire problems. I've installed both but still have the same problem (others have also confirmed the patches don't help).
I suspect it may be an incompatibility between this chipset and certain video cameras. I had a similar problem a while back with a firewire card in a different computer. When I replaced the card with an older firewire card with a real TI chip it worked great.
It's just hard to believe ASUS doesn't even have a FAQ or knowledge base article about this problem.