PROBLEMS: 2x EN9800gfx TOP vs Stirker II extreme mobo vs Corsair 8gb

Ok,

So I just bought a new computer.

Specs:

Asus Striker II Extreme
2x Corsair Twin3x 1333mhx DDr 4GB
2x Asus GeForce 9800GX2 1 GB "TOP" GDDR3
MIST 1000w PSU, Detachable cables.
--- Windows Vista 64bit.

4x Sata disks
1x DVD writer. Connnected to the IDE slot.

Been a while since I did buy a new system, last time about 3 years ago.

Im having major stabilty problems on this new one.
I just cant figure out what it is.

With both cards running in SLI the computer crashes after 10-15 mins inside Bioshock.
With just 1 of em running, the system last for 1 hour.

Somethimes it ever crash when im just surfing the inet in windows.

I have tried:
- flashing the bios to the newest version.
- changing the voltage on the RAM.

Also when I boot up, the LCD poster tells me: DET IDE (detecting IDE) and then displays "ERRORMSG" for a brief second and continues to boot windows.
I tried to pause the bootup at that exact second, but I dont see any errormsg on the screen.

The PSU have 3x 12V1 3x 12V2 and 6x 12V4.
What outtakes shall I use for the GPU?
- The GPU has 2 power intakes. 1x8pins and 1x6pins. Both of the need power.

Im really struggeling with this,

All help would be useful at this point, im totaly frustrated.

Thanks for the replies.