The next step I would take would be to boot to a linux distro something like Mint: http://www.linuxmint.com/download.php
See if after a shutdown with linux the same issue happens.
If it does, my next step would be: start removing all non essential hardware (will require taking the computer apart) hard drive, wireless card, keyboard, touchpad, webcam, etc. Then use a usb keyboard (if you do not have one, use the built in keyboard) and boot to linux again, shutdown and try to power on. It could be any hardware device causing the computer to fail to power on. I suspect it is a mainboard issue, but it could just as easily be another component...
If you remove all of the hardware except: cpu, cpu cooler/fan, ram, built in monitor, and the power cord (leave the battery out), and you still have problems getting it to power on, something with the remianing components has a problem.
Edited by zingo156, 06 April 2014 - 11:06 AM.