IOH Overheat Problems

Hey guys, long time lurker, first time poster. Anyways, the past few days my machine has been shutting down due to IOH Overheat. So i proceeded to down-clock back to factory defaults, and now I still occasionally get shutdowns. I'm set-up on a Rampage III Extreme, 975-ee, and a Sapphire 5870. Any ideas?

Have you put the IOH fan on?

Yes, sorry I forgot to mention that. Yea, I also put on the extra heat sink that has the 40mm fan attached on it. Also, the thermal paste looks just fine.