** Idk if y'all solved your power problem, (I realise this thread was started over a yr ago) but the same thing was happening to me. I found a bizarre solution that absolutely worked and continues to- still.
You have to heat up the power source to the computer, i.e. heat the cord where it goes into the back of the tower. It's kind of a pain so I leave my computer on all the time to avoid having to do it but if the power goes out this is what I've been doing (ever since I read this online somewhere a couple yrs ago):
** Get a blow dryer, turn it on high/hot setting, and aim it at the back of your computer tower where the power cord plugs into it. Hold the blow dryer ~3 inches away, or however far u need to so the blow dryer doesn't overheat from hot air blowing back at it (which, if this happens, u hafta let the dryer cool off for a while- I speed things up by blowing hard into the mouth of it 5 or 6 times till it comes back on).
- Sometimes it takes 1 minute of heating the power source b4 my computer will power on and sometimes it takes 4 min. Since I hate having to stand there holding the blow dryer and pressing the power button every 20 secs to see if it will turn on, I turn on the blow dryer and set it on a pillow I put behind the tower. I arrange the pillow so that when I set the blow dryer on it, it's is at the right height, positioned so that the hot air is blowing out a few inches from where the power cord goes into the back of the tower, and then I leave it alone for a few minutes. When I come back in and press the power button, it lights up and my computer starts every time. Yes, it sounds retarded, I know.
So that's it. When I read this solution I was 99% doubtful myself, but since nothing else worked to get the dang thing to power up, I figured I had nothing to lose. It was crazy great when I pressed the power button and it stayed lit, and I said "Thank-you Lord!" when my monitor lit up a second later. :-D