>>         I've been thinking about this for a week now and I'm not sure I
>> understand.  I thought resistance always increased with increasing
>> temperature.  The basic idea being that as you heat something up the
>> mocules move around faster making it that much harder for the electrons
>> to move through the conductor which is in effect increasing the resitance.

At room temperature, silicon is almost an insulator because it has no free
electrons to conduct current with.  The only electrons available to conduct
current are those produced by impurities (such as the dopants used to make
"P" and "N" regions), flaws in the crystal and the electrons that are
knocked off a silicon atom by thermal effects.

As the temperature rises, more electrons get knocked off the silicon atoms,
which lowers the resistance of the silicon, which leads to more current,
which heats up the silicon atoms still more, knocking off more electrons,
which lowers the resistance ... this process is called "thermal runaway" and
if external circuitry doesn't limit the current, it turns the silicon chip
into slag.

Dave, N9LTD