Sometimes when you run more the one app (in windows) that reads temperatures, it may screw up.
Try the same thing you were doing, but in the bios. You said the CPU temp was reading 120C. That would have to be the Tcase sensor, which the bios uses, and that the core readings are on a different sensor, on the tjuction.
It isn't nothing to do with bad assembly or bad cleaning conditions, this is a 1 month old system, which was working fine.
I did an update to the P5Q bios, lets see if it fixes anything, and i enabled the C1 state thing on the cpu settings, i don't like seeing it constantly changing frequency, but i'll have to use it just to test.
The damn cooler is annoying me, cause above 1200RPM it starts a damn irritating noise, like something vibrating, from what i can see, it's something inside the fan.
I have had a similar problem with my motherboard. I was specifically using "Everest" to monitor temps under load. For me, it turned out to be a problem with Everest. No other heat monitoring software caused the problem for me. Ever.
The Cores would always show at normal temps, but the "CPU" would show extremely high temps. I even went as far as contacting XFX about it thinking my BIOS or mobo had a bug in it. Basically all they did was accuse me of altering the voltage settings on the motherboard. Even though I kept telling them this occured while everything was at default settings & stock speeds.
I stopped using Everest, and haven't had this problem.
It did appear to be related directly to the motherboard's reading of the Tcase, where as the CPU Cores are read directly.
If you're having the same problem I am, it is imaginary. If your CPU was really at 120 to 150 C it would be toast. To to mention you could feel the fan (if case is open) and it would probably be hotter than crap. Plus that Intel CPU would probably go into thermal mode and shut itself way down.