did you uncomment the /sbin/modprobe line in /etc/rc.d/rc.modules??
personally I don't use that particular AGP, I use the one supplied by the Nvidia driver, so.......do this
in your xf86config file, add this to Section "Device" right under the Driver "nvidia"
and just leave the AGP line in /etc/rc.d/rc.modules file commented out.........
post back on how this works out for you.....