amd64, tnt2, xorg, odd behaviour

[cathalferris]

I am running gentoo-64 on an amd64 3000+ (s768) using a msi k8n neo platinum. Graphics card is a tnt2. Kernel is gentoo-provided 2.6.9-r12.
Using the nvidia driver, I get a black screen and functioning cursor, but no visuals other than this. I can run glxgears and that shows. If I have the splash screen enabled, that stays in the background.
Using the nv driver, all is fine.

Is there a known issue for this combination of hardware/kernel etc?
I searched the forums, but there were only references to 2.6.10 and pci-e, and different behaviour with older gpus, not this behaviour.

Thanks