first disable Desktop 3D effects (no compiz)
then remove them ( any dkms-nvidia packages)
also you can remove any x11-driver-video-nvidiaxxxx too
just leave x11-driver-video-nv and x11-driver-video-nouveau untouched (installed)
then reboot
the X Server should start normally
tested on my pc with a N-Vidia FX6200 (older than your card

)