[artdrivers]

It does not matter if you did this before. The first thing I would do is not install it until you get a P.O.S.T. Bench test out of the case and off chassies for P.O.S.T. You could be getting a short from the case. We recommend removing that motherboard from the case/chassis and test the board for POST. Please follow the following simple steps.
1. Place the motherboard on top of the cardboard box (you can use the motherboard box)
2. reseat and or install a good CPU, good CPU fan, good Memory, good power supply (plug the 1 X 20 pin and 1 X 4 or 2 X 8 pin from the power supply unit) and a good video card.
3. Hook the monitor to the video card and be sure the monitor is switched on.
4. Turn on the system board by using the good case "Power on" switch.
If the system fails to POST, check the components' insertion again to ensure they are all connected properly. Try to refrain from adding any drives or usb connections or other parts that may cause a failed P.O.S.T.!
These are instructions from Gigabyte. Try this and let us know how it goes. If no P.O.S.T. try this while it's out. Have you reset the bios? Have you tried checking that board with a different power supply or Graphics card or memory or cpu? Perform a thorough inspection on all the parts. If you try all of the above and no P.O.S.T. Then you may want to RMA the board.