This has been a problem (& reported to Piriform) since at least Feb 2012. I was disappointed that this hasn't been fixed in the current release which is reporting the motherboard temp as the AMD processor's temp.
The speccy reported processor temp is about 15 degrees lower than the Asus utility shows. The MB temp doesn't appear to be captured by speccy & maybe this is a good thing to avoid worries about imminent combustion!
On another PC with an intel i3 processor and a Gigabyte MB the reported temps look ok.
This is buggy software but it's free so what's the point in complaining but beware if you have an Asus MB or an AMD CPU or, gosh gasp, both!
AMD Phenom II X6 1040T 18 °C
Thuban 45nm Technology
ASUSTeK Computer INC. M4A88T-M (AM3) 33 °C