You might want to be sure you have a case fan pointed at it. I never had a problem with overheating on my 975X Platinum, but I had a VF-900 blowing air from the graphics card up that way and my Zalman cooler hung over it a bit, so you may just be lacking airflow now, try pointing a fan at it if you can.
the 8800gt vents hot air back towards the hdd not outside but also not towards the northbridge.
got a big 250mm side fan on the case so there should be plenty of airflow.
and i have been thinking of the "Ghetto mod" solution too.
but i would like to know why it is suddenly hot, to hot to touch.
when it has been used for 18mths with no problems untill the gfx card change.
i will try and get a digital thermometer on it and find out just how hot it is.
chip sets can take allot of heat. so don't be worried if you see 50 or so...With your side fan, i would not worry. when you open it its most likely warmer then running it closed.