I'm sure that jetcollie's link is likely to be the most fruitful - having had 2 ASUS mobos, I can attest to the fact that what their specs say they can do and what they actually support can be rather different.
I'd be surprised if the CPU could be overheating in the few minutes - seconds really - that it is running. But you should certainly make sure that the old paste is removed and new applied before finishing the build. When it is up and running it's going to be HOT (it's an AMD).
SD