Asus P5B-E POSTing issues

[Anusha]

My old P5B-E is having trouble POSTing sometimes.

Weirdest thing is that cold boot works fine. That means, I turn ON the UPS and then straight away turn ON the PC.

But when I turn ON the UPS and keep the PC OFF (but mobo still powers up because of ATX) for some time, and then try to turn ON the PC, it would fail to POST. Turning the UPS OFF and turning it back ON doesn't work. I have to keep the UPS OFF for about couple of minutes before turning it ON. Then the PC would POST, but again I should not give it much time to go nuts.

What I mean by NO POST, is not even a single BEEP. When that happens, even if I take out all the RAM and turn the PC ON, it still would not beep, as in it doesn't even get to that point. But the fans and HDDs and everytime power up. Weird!

Looks like a power capacitor problem eh? It gets charged incorrectly or overcharged whatever...What do you guys say?

P.S.
It has nothing to do with OCing. I have overclocked, but this even happens with stock settings.

 

[Cuzza]

I say try a different power supply. If that fails, new motherboard. Let's face it, you WANT to buy a new one anyway.

 

[Anusha]

I say try a different power supply. If that fails, new motherboard. Let's face it, you WANT to buy a new one anyway.

Hehe. I want to, but I'd rather spend that money on something that give more tangible gains.

I don't think it is the PSU though. See, this problem is new. I never had the UPS turned ON without the PC being powered up. But recently we got IPTV and the router is plugged through the UPS as well. Dad comes home and turns ON the router to watch TV and the PC also gets power. But it is not switched ON, as in pressing the power button.

The PSU has a power ON/OFF switch at the back and in the last few days I switched off the power from there as well, so that now when the UPS is turned ON, it doesn't give power to the PC. But today I forgot to do that and let's see what happens today.

I asked this question mostly to know about what's causing this, not for a fix. The fix would be to take the mobo for RMA (it will be quite a difficult thing to explain my problem to the shop guys though) or buy a new mobo. But the problem is, S775 is aging and I don't want to spend about $130-150 (P35's are around that much in Sri Lanka. sucks I know!) for a new mobo.