4870x2 Crossfire Overheating/Shutting down

Hey guys, I need some help with my quadfire setup. I recently replaced the coolers on my sapphire and msi 4870x2s with Arctic Accelero 4870x2s.

Each card shows drastically reduced temps alone. However when I crossfire them the top card gets really really really hot, so hot I cant take it out of the case for a while, the bottom card is barely warm to the touch. As a result when I have both cards in the case my video has as tendency to completely blank out after 15-30 min but I can see the rest of the computer is still running (HD lights flashing, etc). The core temps are in the 40-50c range but the VRMs of the top card in the mid 50s to 60s C.

I have tried switching them around to no avail, the top card always gets super hot and (I think) causes the computer to crash. Another factor is that one is running at 780mhz/900mhz and one is 750mhz/900mhz, I have tried using overdrive to bring them down to 750mhz each but nothing seems to be helping! Is there something I am missing?