This issue appears to be identical to the one reported here:
http://lists.opensuse.org/opensuse-amd64/2007-04/msg00001.html

By manually adding mem=4096M to my boot line, the system is able to
come up fine. Otherwise, it will randomly hang during boot after the
line:
agpgart: detected an Intel 965G chipset.

This is a Gigabyte GA-965P-DQ6 motherboard at the latest F10 BIOS
level. The full dmesg output from a working boot with mem=4096M is
attached.

Thanks -Andrew