I have the exact same problem. Using ECS A885GM-A2 Mother board. with one card in either PCI-E slots power down works fine. However, with two cards installed it will attempt to do a powerdown and the within a second or two power up. The driver on the motherboard during pwr down cycle brings the Pwr_on signal on the ATX power supply high (power off) then immediately down low (power on) and remains there. You can even turn the atx pwr supply switch off so only the standby power is applied to the mother board and the motherboard is still driving pwr on low (power on) to the ATX supply. When you switch the atx pwr supply switch on it immediately boots. Have disconnect the pushbutton power on button and same issue. Also tried 2nd power supply. Any help or ideas here would be appreciated. Also disabled init 13h on a single board and then both boards, no luck, still there.