Comment 9 for bug 109643

RJ:
Good catch! I guess I had better starting asking more questions! : ) Can you re-enable "cool 'n' quiet" in the BIOS and add the following new line just after #! /bin/sh in /etc/init.d/powernowd
exit 0

This will basically disable the loading of the program that changes the speed of your computer at boot. Can you then see if things still lock up after a while?