Athlon 1.2 Freeze ups?

I'm not sure where to post this...

I have a DFI AK74EC mobo with Duron 700mhz and just upgraded to GeForce4 mx 440 and Athlon 1200mhz cpu. Installed and boots just fine. I ran SISandra benchmarks ok. To stress out the new graphics card I fired up Medal of Honor at max graphics settings. It flies for about 15 minutes then the screen freezes, requiring a reset.

At first I thought it was temperature of the cpu, because after one reboot the bios monitor showed about 135 degrees F. I tore out the fan, scraped the insulating gunk off the heatsink and reinstalled. I also added a chassis fan and tried to clean up the inside cables. It seemed to help, as I got it down to about 105F or so (I understand it heats up with intense activity), the range of my Duron 700.

I'm still getting lockups, and not just in 3d games. It also happens in normal use surfing the web, etc.

I can return to the Duron 700 with no problems even with the new Graphics card.

I've seen a couple of posts on the net about possible AGP problem on the VIA chipset.

Any ideas about how to figure this out? DFI has no info on their website (I emailed their tech support; no answer yet).

Thanks,

Tim