Im not sure about the BIOS Flash however you would really need to refer to their Tech support for more information why the mobo doesn't support that CPU without a Flash.
I don't think it would cause the Power to go off after a few seconds though.
Trying booting with only RAM, CPU and Video card.
If it still doesn't work then try motherboard out of case on a hard surface. Again with only CPU, RAM and Video card.
Make sure Motherboard has the 4 Pin an 24/20 Pin connector installed and properly connected. Make sure if video card has a molex connector that it is connected.