What does the BIOS temperature monitor look like?
I once owned a k7s5a (for a very short period of time) and had no problems with it. It has since found a home at a friend's house, and is running quite well, despite the conditions.
For the money, I liked it better than the GA-7VRXP that replaced it, though I have since switched back to ABit boards.
Side note: I haven't really been keeping track; did ECS release a nicer BIOS for the thing? I recall having to flash to an older BIOS to get any overclocking options at all.
EDIT: In answer to your question (

), unless somebody really goofed in the revisions since I owned mine, the fan should not cause such horrible swings in the temp readout (barring a dying fan on an air-cooled setup

).