Re: GLX causes X server crash on Geforce6600+6.1-RELEASE-p3+xorg6.9.0+nv1.0.9746
I agree with adamk75, Xorg is loading the wrong glx module.
I had it happen once too, I solved it by pkg_delete nvidia-driver-1.0.9746_1[*], rm -rf /var/db/ports/nvidia-driver/ (this removes previously set build options). Also have a look in /usr/X11R6/lib/modules/, drivers and extensions, remove any leftover XXX-* files.
Then rebuild & reinstall the nvidia-driver, cd /usr/ports/x11/nvidia-driver/ && make all install clean.
[*] replace with your installed version, have a look in /var/db/pkg/ to see which one is installed.