Broken touchpad = unable to boot ?!?

Ok, this is the second time this is happening to me, and the first time this happenend, it apparently solved itself. I hate :evil: self-solving problems with a passion.
Anyway, the problem manifest itself this way:
- suddenly, while you are working with the AAO, the touchpad stops working.
- You verify that you did not hit the dreaded Fn-F7 by mistake to no avail.
- Plugging an usb mouse is you only way out.
- You thus finish doing what you were doing, preparing to (hopefully) reboot the beast into a better state (you fool) Something is definitely amiss, because the windows XP shutdown sequence does not goes well, practically _everything_, including the Systray (?!?) has to be manually killed, and finally you power off the thing after staring at the same "windows is shutting down" screen for 10 minutes. After that everything get worst.
NOTE: after one occasion where WinXP installed itself into oblivion, I multi-booted my AAO with a few options:
* Ubuntu 9.04
* Memtest 86
* a dos prompt to be able to do NTFS FSCK/WinXP reinstall
* Win XP
What I have now (and why I'm in despair):
- Booting Ubuntu from the HD (or even from my trusty USB key) lead to an IMMEDIATE SHUTDOWN: as soon as the startup scripts displays "loading file needed to boot" BAM, the :twisted: thing shuts off !
- Booting Windows XP eventually brings the thing into a state where the disk activity comes to an halt, and the activity bar under "Windows XP" moves jerkily. And stays there.
Booting into Memtest works fine, and into dos as well. For instance I can dos a ntfsck on the WinXP partition, which seems fine. But any OS worth its salt just does not work.
I tried reinstalling the bios, I tried shutting down the thing and removing the battery for a long time, I tried loading the BIOS default, I tried plugging in an USB mouse to no avail.
The only thing I don not want to try is disassemble the thing, I do not want to void the warranty (but I'm tempted).

Any taker/advices ??? I'm desperate.