I have P35 (Gigabyte GA-P35-DS4 Rev.2.0 with BIOS #F11) motherboard, a Intel C2D E8200, 1GB DDR2 x 4 and nVidia 8500GT. I encountered a system freeze when startx was executed on FreeBSD 7.0-RC1.
I use the modified kernel which is enabled some debugging option.
But I can't get a memory dump because keyboard was not active and couldn't enter kdb mode while system hang-up.
This problem appear when "kern.smp.active" is set to "0" by sysctl.
I try the new version of nvidia-driver (169.07) with modified ports. But the problem is not cleared.
Attached bug report contains /var/log/Xorg.0.log. That Xorg.0.log was generated when startx is executed without nvidia.ko module. No Xorg.0.log was logged when system hang-up.
If you can read Japanese, please refer to my article: