Luxor horribly jerky on Athlon64+X700Pro?

[Damien]

I've got an Athlon64/3000 on a Gigabyte nForce4 SLI board. I originally had the Geforce 6200 128mb non-Turbocache PCI-E card but it crapped out so I replaced it with an ATI X700Pro. Everything seems fine, except for one thing: the game Luxor now runs like crap. It used to be really smooth but now the screen stutters like all heck! The game runs on a P2-300 so it isn't a horsepower problem, my guess is something in the drivers.

Just to verify it wasn't the card itself I tried Quake 2, which runs smoooooottth, so no problems there.

Any suggestions on what to look for?

Thanks.

Damien