Your symptoms usually indicate a power supply problem, or a short circuit, which should not occur with the board set up outside the case.
Do you have the eight pin CPU power cable connected to the board from the PS? Be sure you are not using a PCIe cable, the six + two pin cable for video cards. Your PS has what is called a four + four pin CPU power cable, which must be used.
Can you test with another PS, or test the new PS on another PC?