Getting yo-yo temps on a Pt6 Deluex V2

Last week I build a system using the P6T Deluxe V2.
Running the ASUS probe with the stock Intel cooler on a 920 I am seeing some wide variations in the CPU temps.

Setup is as follows.
VGA SAPPHIRE| 100269SR 4890 1GB

CORSAIR|CMPSU-750TX 750W

2Gx3|CORSAIR TR3X6G1600C8D

INTEL|CORE I7 920 2.66G

ASUS P6T DELUXE V2 1366

The issue I am seeing is that I will get a wide jump and fall in temps even when the system is not under load.
Last night I had WoW, firefox and vent up and running only. With wow up in a windowed mode I was seeing the temps go from 51C (Mobo temp was 49c and held steady all evening) to 70C, if I was minimize the wow window I would see a CPU temp fall of at least 5c within 10 seconds, bring the wow window back up and it would jump again.
The CPU load never got above 10%

This does not feel right to me and I am trying to work out if it might be a sensor issue or if I am getting overheating issues.

Any advice anyone can give would be appreciated.

What kind of case do you have? One with poor ventilation will allow heat to be trapped by the video card. I am seeing that problem in several cases. One possible quick fix if it is indeed a heat trap by the vid card, is to get a PCI slot cooler and mount it under the vid card to aid in heat removal.

Just to verify, when you say "10% cpu load", you mean total usage? If so, that is normal, i7 has 8 threads, so 100% / 8 = %12.5 per core. So a "12.5% cpu load" is one core fully loaded up. You could also try disabling Hyperthreading, which should increase your framerate a bit.

GrimX9, I reused my chifetech dragon case for this build and have all 5 80MM fans installed and running.
Fan config is 2 on the front, one in the bottom one over the hard drive bay, bottom fan is unobstructed, one side intake fan pushing air in over the graphics card and 2 exaust fans on the back of the case inline with the CPU fan, the PSU has a 140MM exhaust fan as well.

thideras, yes I do mean total CPU load of under 10% according to task manager. CUP load was sitting about 6%-8% most of the time while I was running wow.

I pulled the heatsink off and found that the thermal compound had large voids in it on one side and a large lump on the other.

I cleaned it all off and seated everything again, now I am getting temps under the same load as before but now I am topping out about 40C.

Maybe now I can look in to a good after market cooler so I can give this system a push to see what I can get out of it.