I am not sure if this will help much, but I used a cheap camera phone to take a picture of some of the messages I see when booting Ubuntu 6.06 with APIC enabled on my system. The last message I see before the reboot (that is if I snapped the picture in time) is "Checking if image is initramfs......it is". Right after that line or so is when the system reboots when APIC is enabled.
-- Boot fails with APIC enabled on an Asus A7V8X-X Motherboard https://launchpad.net/bugs/70774 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs