solution, so here's my little saga.
The system:
AMD Athalon 1.533 GHz
768 MB RAM
ATI-powered 9500 card, Catalyst 3.2 drivers
I recently upgraded my machine to the above configuration. N2K3 was
running fine until then. Now it will occasionally crash in the middle
of a race, dropping back to the desktop. The only thing I've noticed is
that it seems more likely to do this if I make a lot of adjustments in
the garage (going back and forth from a practice session to get the
setup right).
I've upgraded the power supply and added a fan. Temperatures are fine,
so I don't think this is a hardware issue of that nature.
Any suggestions?