The nvidia-drivers ebuild checks if glibc is built_with_use nptl, which gives an error for glibc 2.6 since this USE-flag does not exist there.
This will be removed; use x11-drivers/nvidia-drivers-1.0.7185.
You're using a local overlay. 7184 doesn't exist in Portage. http://sources.gentoo.org/viewcvs.py/gentoo-x86/x11-drivers/nvidia-drivers/ Look at the 7185 ebuild: built_with_use --missing true sys-libs/glibc nptl
*** Bug 186659 has been marked as a duplicate of this bug. ***
The comment which suggest loading nvidia-drivers cannot work since the non-legacy drivers won't work with those older cards which require the legacy-drivers package.
(In reply to comment #4) > The comment which suggest loading nvidia-drivers cannot work since the > non-legacy drivers won't work with those older cards which require the > legacy-drivers package. x11-drivers/nvidia-drivers-1.0.7185 works just perfectly fine w/ legacy cards, you didn't try at all.