BIOS Health Screen locks up

A friend has a P4 1.8 Northwood on an Aopen SIS 645DX board. When I boot and go to the BIOS and Health screen I get no reading other than CPU 265 degrees. Hitting the Esc key does nothing and I must use Ctl Alt Del to get out of this screen. I put in Aopens monitoring software and as soon as windows boots I open it and it says CPU 69 C System 72 C. Now I know that this is nearly impossible and I am pretty sure that it is a problem with the Winbond chip and think I sould RMA the board. I have run AMD on my own system and am really at a loss to explain what is happening. Please help am I right in my assumption or am I missing something here. Thanks.

Just a shot in the dark but unplug all fans that are plugged into the motherboard that have a 3rd wire on them [tach wire] and try it. I have seen bad/shorted out tach wires screw up BIOS navigation.