I have been using the driver from nviida, not the gentoo ebuilds, so no.
some people seem to think this is a bad idea, but i have yet to have a reason why. The only problem I can see is a minor difficulty when trying to update X through portage.
I have just solved the problem, if anyone is interested, by disabling 4k stacks and recompiling the kernel.
Thanks for the suggestions, in any case.