Oops! Turns out I don't have the latest drivers on my gentoo system - they haven't updated the ebuild yet (for my profile anyway). So I'm using 1.0.4349 there.
I use gaming-sources 2.4.20-r3, but I've used gentoo-sources and ck-sources before with no problems (not sure which nvidia driver versions though - I run emerge -u world just about every time I boot gentoo
I'll try 4349 on LFS to see if that fixes things.