Since all we can do right now is grasp at straws. We just have to start somewhere and work from there. Go ahead and start by reducing the voltage and Mhz of the CPU to their factory default settings, be sure that your PCI bus is locked back to the normal 33Mhz. Try running that for a while. If that doesn't work, my next recommendation is to run a program called memtest86 which you can find at:
http://www.memtest86.com/ This program will take a while to run, let it run at least overnight so that your ram and CPU can get up to normal working tempature for a while. After all of that is done, we can start playing the hardware swapout game.