Hi there,
I had the same thing a few weeks ago when trying to get my computer to stop locking up!
I ended up taking out all the pci cards and messing around with the BIOS.
It stopped looping when I set the Power Management setting in BIOS back to APM/ACPI.
It's a long shot, but it got my PC booting properly again.
I haven't found out yet what is making it lock up though. Seems to happen when the drives are being accessed and at purley random times!