With the above comment on an external fan I bought a boxfan for $18 from Walmart.

The side of the case has holes in it, so I put the boxfan on the side of the case and blow air in. The key is to have the airflow from the top, down on the GPUs.

At least for my setup, this avoids the heat trap. I tried blowing air from the front, but it did not do much. By having the air blowing in from the top of the graphics cards, it basically blows the air away from the point source, that would be the cards themselves. I saw about a 4 degree C reduction on the hot card (I have two) and a 7 to 8 degree reduction on the cooler card. The box fan pulls 70 watts from the wall (I have it on low, which maybe 40 I can't remember).

Probably the easiest quickest way to save some life on your cards.

You can check Cgminer to see if you are having any success. Keep moving the fan till you get the best cooling solution. Also, higher flow of air, does not mean cooler gpu.

--GarbageName