I added a hard drive to my file server this morning and after plugging it back in, I pressed to power button and the power button flashed and the fans started to spin up, but it just immediately turned off. I tried a second time and was met with the same result. My power cable was coming from a UPS, so I tried plugging it in directly to the wall. This time, as soon as I plugged it in, the PSU started up and kicked on all of the fans, but the system didn't post. I thought that maybe my power button was screwed up and permanently closed. However, I tested the connector with a meter and it was fine and even without the atx switch connector plugged into the mobo, the psu would still auto turn on when plugged in. At this point, I figured it had to be my PSU so I ripped the one out of my desktop and tried it. This PSU didn't auto turn on when plugged into the wall and it didn't turn on when the power button was pushed either. As a last result, I pulled the mobo and with ONLY the cpu and memory (no vid card) I placed it into an empty case with a third different case. I didn't expect it to post since I didn't have a vid card plugged in, but I wanted to see if a different power switch would help. It didn't. I still had the same issue where nothing turned on when I pressed the power button. Does this sound like a mobo problem? That's what I would guess. I checked the traces under the atx switch pins and didn't notice anything.