i've had thinkpads freeze.  i suspected the disk and/or bios power management interface.
i don't enable apm on the thinkpad but even tickling it in the initial load
seems to change the bios's ability (that's to say that the old system that
left it alone allowed the bios to do some things, i suppose with the smi
interrupt, and now it can't reliably do all that it did).

more specifically, the disk activity light is on, the (soft) power switch on
the thinkpad doesn't work, and i need to prod the little button hidden inside
to get the machine back.