I have raised a query not long ago but will post as much more info as I can...

The computer I have put together 1 by 1 inside an Antec 1200 case, including the new parts on the order:

Gigabyte Z68X-UD5 motherboard
Intel Core i7 2600K CPU
Antec Kuhler H20 920
Corsair Vengeance RAM (2x4GB CMZ8GX3M2A1866C9)
2x AMD Sapphire HD5850 1GB Toxic edition with crossfire bridge
Auzentech Forte X-Fi 7.1 soundcard
2x Intel X25-M 80GB SSDs
1x Samsung Spinpoint F3 1TB HDD
LG GH22NS50 DVD Rewriter
Corsair HX1000W power supply

Here are the steps of what I did once the build was finished:

1) Powered the computer on and went straight into the BIOS.
2) Successfully flashed the bios from F3 to F8 as provided by Gigabyte's website.
3) Rebooted the computer and changed the boot order in the bios to CD, HDD to install Windows 7 64bit. Saved bios and rebooted the computer.
4) Configured the 2 Intel SSDs to RAID 0 using the Ctrl+I option.
5) Rebooted computer and proceeded to Install Windows 7 onto the SSDs.
6) With Windows 7 now installed, I changed the boot order back and installed all the correct latest drivers, in Windows, for the motherboard as provided by Gigabyte's website.
7) Shutdown the computer and left it overnight. The next morning the computer powered on and as it got to the Windows 7 loading screen the computer froze and rebooted by itself, got to the initial post screen and then rebooted again this time with no display and rebooted again and again with the computer only being on for around 5 seconds before powering down each time.

So now all that is happening is the computer powers on for 5 seconds then powers off and keeps doing this until I switch the power supply off. While this is happening there is no display (monitor is just on standby the whole time), no beeping of any kind or any abnormal sounds, all fans are running including the CPU cooler fans and graphics card fans.

All cables are correctly plugged in and everything looks like it should work. I have built 3 computers previously with no problems so I feel I know how to go about building a computer in the correct way and everything to check to avoid any problems in the first place. I did notice since the first time I accessed the BIOS (versions F3 and F8)of this computer that some of the text flickered now and then and some of the screens seemed a little sluggish.

Here is a list of things I have tried to rectify my problem:

1) Disconnecting power to the computer and pressing the reset CMOS button.
2) Removing the battery of the motherboard for 1 minute to try and clear CMOS.
3) Connecting the power supply to 4 different wall socket outlets and 2 surge protected extensions.
4) Swapping the power supply with a Corsair HX620W power supply and also swapping the modular cables.
5) Checking the motherboard for any short circuits or visible damage. None found.
6) Checking the CPU for any surface damage or bent pins and also the motherboard CPU socket connection for any visible damage. None found.
7) Reseating CPU and CPU cooler. Thermal paste looks like it made perfect contact between the 2.
8) Disconnecting and reconnecting all cables and checking for any visible damage. None found.
9) Disconnecting all but essential hardware.
10) Swapping the RAM to different banks and trying with just 1 stick.
11) Trying both graphics cards in each PCIE slot 1 at a time.
12) Connecting graphics card to a different monitor. Monitor still stays on standby when computer powers on and off.

I think that is everything and still the same happens each time which leads me to believe to my knowledge that either the motherboard or perhaps CPU are faulty. I can't think of anything else to try with the hardware that I have so I'm asking for help as for what to do now. Return 1 or both parts to SCAN for checking/replacing or RMA them to the relative companies. Both items have their warrenty stickers intact.