Wow, this post has been up so long I'd forgotten about it. It turns out that what you are looking at is the temp of the Northbridge (X58), there is no "MCH" (Memory Control Hub) as this task has been taken over by the i7 CPU. The Gigabyte BIOS needs to be rewritten to correctly identify the chip.
In my experience Gigabyte did a less than adequate job dealing with heat on their UD3R MOBO but it's OK, even getting 60 C at idle since the chip is designed to operate above 100 C. This temp rises as you overclock.
To solve the problem on my MOBO I pointed an 80 mm fan at the heatsink and dropped the operating temp at idle by 10 - 15 C. My next step will be to put the Northbridge, Southbridge and vRegs under water.