Thanks for this!

Probably a better idea to just increase the fan speed or just replace the cooler entirely.

Its a bug that when you're in any type of menus (be it pre-brefieng, post-brief, menue after cutscenes, etc.), your GPU will automatically render everything animates on screen without a limit.
Where as the stuff going on screen are just very minimal, over a period of a few minutes your GPU will overheat.

The solution to this is simple, just go to:
My Documents > Starcraft II > Variables.txt

Under the command line: foliagequality=x (this depends on your Terrain setting)

Add -
frameratecap=60
frameratecapGlue=30
You can set the framerate cap to 70 or 80, up to you.
But really they are menus... why in god's name would you even want anything more than 60 (heck, 30 for that matter).

Of course, increasing your fan speed will also bring temperaturs down as well as playing in an air-cond room.

My single-slot first-release 8800GT (which is known to be freakishly hot) OC'd to 700/1000 only reached 80c in a non-aircond room, afternoon time.