The nvidia guide (I can only select the nvidia trouble shooting guide as component to file this bug-report in, while the guide is called "Gentoo Linux nVidia Guide", so sorry if this is wrong) doesn't mention that it might be useful to add "nvidia" to your useflags in /etc/make.conf . The useflag isn't documented in the online list of available useflags as well (see http://www.gentoo.org/dyn/use-index.xml ), but used by xine-lib as well as mplayer ebuilds. AFAIK the useflag enables nvidia's XvMCNVIDIA which is useful when watching movies with high resolutions. Perhaps the nvidia ebuild (nvidia-kernel, nvidia-glx) should provide the useflag as well(?) don't know Reproducible: Didn't try Steps to Reproduce:
Updated doco in CVS.