Problem with K9N DIAMOND at boot

Question

Hello,
I've a problem with my mainboard K9N Diamon.
I've this configuration :
K9N Diamond
Athlon X2 6000+ with Zalman 9700NT
2x1go DDR 2 PC2 6400 at 800Mhz Corsair DOMINATOR
Thermaltake Thoughpower 700W
Case Thermaltake Kandalf VA9000BWS
GeForce 7600GT Msi
2x 320go WD HDD
Dvd burn LG H42L
So, When I plug the power cable, the pc turn on, but 3sec later it stop. I push the power button, nothink.
I change the alimentation, with a 350w enermax, 500w PFC, 500w thermaltake, nothink.
The D-Bracket tell me no infomation, at the shutdown after 3sec, the led are different at the last boot. Impossible to identify the problem.
I test a 4200+ with 2x512mo DDR2 PC2 6400 at 800mhz corsair XMS2 and NX 6200 msi, but no change. When I plug the power cable it start, and 2 3 sec later it stop.
I reset the bios, with this method :
Code: [Select]
1.Shut Down the PC.
2.Unplug the Power Supply from the AC outlet and unplug the cord from the back of the Power Supply.
3.If your Power Supply has an On/Off switch on the back of it turn it Off.
4.Ground yourself and your PC.
5.Remove all DDR2 DIMMs
6.Remove the following power connectors on your mainboard:
   *JPWR1 - ATX 24-pin Power Connector
   *JPW1 - ATX 12V Power Connector
   *JPWR2 - ATX 12V Power Connector
7.Clear CMOS.
8.Reattached power connectors in Step 6 above.
9.Place a DDR2 DIMM in DIMM3 (the slot closest to the CPU).
10.Plug AC cord into Power Supply and AC outlet.
11.If your Power Supply has an On/Off switch on the back of it turn it back On.
12.Boot the PC.
But no result.
I test the CPU, graphic card and memory on other PC, It work fine.
So, I think the mainboard is broken, I see problem like mine, but it's different here.
I'm for MSI, I've all pc with this material, and all of my friend / custommer, but here I'm disappointed.
This is an problem with a production series default ?  I dunno.
So I I'am for MSI, and I think I'v bad luck in this moment ! 
Sorry for my english, i come from Corsica ^^

Answer 1

Thanks again for your answer and Help.
I've trid to start with just : Athlon 6000+ / 512mo DDR2 .
The system start, 2sec later stop. for restart with power button its impossible. I change the power button with reset button, same problem.
I test with an screw driver, the system start when I plug power supply, and after 2 3second stop. I test to start with screw driver, I similar... but 10sec later, after short reset, hdd led, its start, for 2 3 sec ! LOL. To restart again, I did short reset, hdd, led, hdd, reset, power, reset, .......... and at one moment its star 2 3 sec !!! Dor restart I do it again. LOL.
It's very strange. When its want , it start ! U_u
So tomorrow, I contact my supplier to change the mainboard ^^ !
I think its the only solution !
Thank again for your help, If you have many idea, I take that again :p
See you soon