I just assembled a new system and it does not power up. It as a Gigabyte m/b (P67A-UD3-B3). Power switch to m/b pins - check, A/C power to power block - check, CPU fan connected to m/b - check, ATX 6-pin and ATX 24-pin on m/b connected - check. What am I missing. Do I need plastic standoffs between m/b and case? On my last system upgrade when I switched from conductive metal to plastic it powered up after similiar situation.