System will not power on

I recently built a new rig...and I went to plug in a headset for Skype. As soon as I inserted the microphone jack into the "microphone IN", the system shut off and will not boot up. I didn't not see or hear any sparking. I'm wondering what steps I should take to get the system working. I have:

1. Unplugged system
2. Waited over an hour
3. Flipped the PSU I/O switch.

I don't get anything. No lights, no fans, nothing. Any ideas?

I'd check all the connections first, and the mobo mounting. Disconnect everything from the PSU except the mobo and video card, see if it posts. If there's a short, the PSU may have shut off to save itself or your system.
Worst case, your mobo is cracked somewhere, maybe around the rear I/O ports.
(can't resist) I'm assuming that step 2a was to plug the PSU back in.
Were there any fan twitches, including the one in the PSU?

Additional steps:

1. Clear CMOS
2. unplug all power i/o on board.
3. use power supply with another MBO (it works just fine)
4. checked green MB LED to indicate power to board (comes on when plugged in).

I think it's narrow down to two things:

1. bad mbo (order GA-P35-DS3L from NEgg)
2. Bad switch...highly unlikely since the only way the switch could have been affected would be for a electrical spark from the headset jack to the power switch, which would require the spark to travel across the bottom 1/3 of the mbo...

Any other ideas?