There you go, proof if proof be need be, that the stock cooler is as useful as a chocolate fireguard. With the bottom max temperature at 54 deg C, I would guess that the surface temperature of the chip top side is in the 58-60 degree region at least. If you have a look at the NB heatsink pic you'll see it is roughly the same temp as the motherboard ambient. This, in effect, is your smoking gun.