Since x11-drivers/nvidia-drivers-71.86.11 and ~x11-base/xorg-server-1.5.3 are masked in package.mask, in nvidia-guide following string is obsoleted: "The oldest NV2x-based cards (such as TNT, TNT2, GeForce, and GeForce 2) require the 71.x drivers (such as nvidia-drivers-71.86.01). For these cards, you should mask >=x11-drivers/nvidia-drivers-87.00 in /etc/portage/package.mask." Instead there must be note that NV2-based cards are not supported by nVidia. For these cards users only can use standard xorg driver nv (or nuveau).
Thanks for reporting. Fixed in CVS.