NvAGP another option
The default AGP choice is to use agpgart and then try nvagp. For my machine nvagp works much better, especially running now on the 2.6 kernel. I suggest trying the nvagp support first, which requires a driver option added into the Device section of XF86Config (where you change "nv" to "nvidia").
Option "NvAGP" "1"
"..the triumph of evil is for good men to do nothing."
VIDIA video driver RPMs for Fedora
:: see yum repo at livna.org