Msi board + 8 gbs ram = Problem PLEASE HELP!

Hey ppls,

I hope everybody is well. I have a problem that i can't undestand or more like figure out.
My Pc:
Windows 7 ultimate 64bit
thermaltake smart PSU 730W
MSI MB P55M-GD41
VIDEO CARD EVGA GTX560 2GB DDR 5
Processor core i5
dvd writer
3 hard drives two 320 gb and a 500 gb

Now currently in the pc I am using 4gb of ram ddr3 (2x2GB) it works fine like this. The MB has four slots, the two 2gb sticks are in DIMM 1 & 3 (dual channel). Pc works fine plays all games on high or ultra settings .

I purchased a single 4gb stick same type of memory (kingston 1333mhz). When i installed the 4gb stick in DIMM slot 2 the computer does not boot. When its insterted in DIMM slot 4, the computer boots fine, but as soon as i log on and start any game with in 15-20 mins the computer restarts itself. btw never had this problem before.

Frist though came to mind is a bad memory stick. So I went back to the same store, I purchased a new 4 gb stick same memory (kingston 1333) to try in which if the other one was faulty i will be given a full refund.

Went home tried the same thing again with the 4gb stick same error. no boot in DIMM 2, boot in DIMM 4 but same crashes.

   

Now for experiment purposes i took out the (2x2gb) and insterted the (2X4gb) one in DIMM 1 & the other in DIMM 3. Computer boots, but same problem as i started a game or any memory extensive application the computer restarts without no warning this time i got a error kernal-power.

I tried on single stick (4gb) one at a time in DIMM 1 computer boots runs normal, plays games etc.

I want to be able to use the (2x4gb)=8GB or even (2x4gb) + (2x2gb) = 12gbs and i cant't.
The MB manual states its able to handle 16GBs if memory (4X4GB)

Any assistance would be great

thanks