Ok this isnt the same problem most folks report
> makes me think there's an APM problem but (i) it's disabled in the
> BIOS and (ii) the time at which the hangs occur is not consistent
it sounds like an interrupt controller crash
> If I'm being dumb please tell me and I'll get off this list and fling
> the 3Com card in the bucket, or build a robot to press the shift key
> once every few minutes.
I think you have a different (and _very_ weird) problem to the rest