NVIDIA 6600GT Freeze

[Nealie]

I have a problem with my system freezing when using an NVIDIA video card
using the nvidia-driver port. All seems to work fine for a while but
then the system freezes and won't even reply to a ping. This can happen
regardless of whether I use openGL or not.

Everything works fine using the "nv" driver, so it doesn't seem to be a
hardware problem.

My setup is as follows:

uname: FreeBSD server.home 6.1-STABLE FreeBSD 6.1-STABLE #0: Wed Jul 19
11:19:16 CEST 2006     root at server.home:/usr/obj/usr/src/sys/SERVER
i386

AGP NVIDIA 6600GT installed on an MSI K8T Neo-F V2.09 motherboard (VIA
K8T800 Pro chipset) with an AMD Athlon 64 3500+ CPU.

The NVIDIA driver is installed as per the instructions, with agp and dri
removed from the kernel in order to use the NVIDIA agp interface, even
though the sysctl settings suggest otherwise.

If anyone has any ideas about this problem I'd be very grateful.