ESX essentially takes hardware information from CIM providers that in turn pull up information from the BMC. So it is either the MB/sensors/BMC/CIM providers - in that order you would need to isolate
I don't see any one else using the same hardware having run into this with ESX - and haven't seen related discussions on the Intel forums - ESX or otherwise which again points to something in the specific device/hardware
http://download.intel.com/support/motherboards/server/sb/g24881004_s2600gzgl_tps_r1_1.pdf
You could check the diag lights on the system board to see if that gives you a clue