aha. this one is a bit trickier
Just that you know, you won't get any 3d acceleration if you don't use the nvidia driver. The nv driver doesn't handle it at all. Have you tried the FAQ thingies with the nvidia driver on ? If not, I encourage you to do so.
Anyway, this could come from the ACPI on (again!) ! At least, it wouldn't surprise me if you had a nforce chipset on your motherboard
. It could come from the AGP thing, either way, so you should give a try to the NvAGP 0 ( or option "NvAGP" "0") in the Device section of your XF86Config file. Could you try everything of the faq again with the nvidia driver on, then tell me the results or particular things you noticed ?