>= 4GB memory and Ubuntu 64

If remapping PCI addresses in the bios doesn't work for you, try adding "blacklist intel_agp" to /etc/modprobe.d/blacklist. What happens is:

"In short, the P965 chipset is being incorrectly identified as G965 (with video) and the intel agp gart driver blows up with PCI remapping engaged."

http://ubuntuforums.org/showthread.php?t=375853&page=2