many crashes of X server, what should I investigate?

[Frédéric Bron]

> The first thing that springs to mind is:  Had the first overheating
> cooked the CPU heatsink goo, and now the chip can't cool down properly.

I manage to go back to normal by unplugging the power unit and
removing the battery pack. It is probably a bug in the BIOS. I am
looking for an update.
However the problem with the X server remains...
Thanks,
Frédéric