I'm trying to configure an ATI Radeon 9000 64mb AGP video card with Xorg. No matter which config option I choose ('Xorg -configure', 'xorgcfg -textmode', xorgconfig), when I test the generated .conf file, the screen locks up with a bunch of colors and horizontal lines (green on top, blue everywhere else). The mouse cursor moves (at least that works), but none of the Ctrl+Alt key combos work, and I can't escape the X session or access another virtual console. The "Device" section generated from 'Xorg -configure' is:
Section "Device"
Identifier "Card0"
Driver "ati"
VendorName "ATI Technologies Inc"
BoardName "Radeon RV250 If [Radeon 9000]"
BusID "PCI:3:0:0"

That looks okay to me, but what do I know? Here's any related output I can think of from 'pciconf -lv':
agp0@pci0:0:0: class=0x060000 card=0x00000000 chip=0x01e010de rev=0xa2
hdr=0x00
vendor = 'NVIDIA Corporation'
device = 'nForce2 AGP Controller'
class = bridge
subclass = HOST-PCI
.
.
.
none9@pci3:0:0: class=0x030000 card=0x20021002 chip=0x49661002 rev=0x01
hdr=0x00
vendor = 'ATI Technologies Inc.'
device = 'RV250 Radeon 9000/9000 Pro'
class = display
subclass = VGA
none10@pci3:0:1: class=0x038000 card=0x20031002 chip=0x496e1002
rev=0x01 hdr=0x00
vendor = 'ATI Technologies Inc.'
device = 'RV250 Radeon 9000/9000 Pro - Secondary'
class = display

I thought it might be an AGP/kernel issue, but when I try 'kldload agp' I get back "File exists", and when I do 'kldstat -n agp' I get "No such file".

You don't want to kldload agp drivers if your trying to install ATI's AGP driver. You want to kldunload agp.

Thanks, but that doesn't seem to work either:
# kldunload agp
kldunload: can't unload agp; no such file or directory
# kldunload -n agp
kldunload: can't unload agp; no such file or directory