System freeze when using agpgart

Running Breezy Badger

I have a dual monitor setup, with a Radeon 9200 AGP (RV280) and Nvidia RIVA TNT2 Model 64 PCI card. What happens is if I try and run both video cards at 1280x1024, about 3-4 seconds after logging in the system completly freezes... Ctrl-Alt-Backspace no longer restarts X, mouse doesn't move, numlock doesn't work anymore, etc....

If I run the TNT2 PCI card at 1024x768 resolution, everything works just fine. Also, if I block agpgart (and radeon, and drm) modules from loading into the kernel (by sticking some stuff into /etc/modules.d), I can run both video cards at 1280x1024.

So, without agpgart loaded, both run fine at 1280x1024, but with agpgart loaded I can run PCI card at 1024x768 but it freezes at 1280x1024. I looked through kern.log, but no oopses are in there. Here is some output from kern.log when loading agpgart

pr 3 23:07:13 localhost kernel: [ 16.814772] agpgart: Detected AGP bridge 0
Apr 3 23:07:13 localhost kernel: [ 16.819005] agpgart: AGP aperture is 128M @ 0xe0000000
Apr 3 23:07:23 localhost kernel: [ 64.092212] agpgart: Found an AGP 3.0 compliant device at 0000:00:00.0.
Apr 3 23:07:23 localhost kernel: [ 64.092225] agpgart: Putting AGP V3 device at 0000:00:00.0 into 4x mode
Apr 3 23:07:23 localhost kernel: [ 64.092250] agpgart: Putting AGP V3 device at 0000:01:00.0 into 4x mode

0000:01:00.0 is the AGP card, and 0000:00:00.0 is the PCI card. My first guess is some sort of buffer overflow in agpgart, when using the higher resolution. I find it odd that agpgart is setting both cards up, when only one is AGP and the other is a normal PCI card.