Boot issues. Wamth?

I've built a rig with the VIA EPIA M2 12000 as base, and I've got some really strange boot-issue. If I reboot my computer, use the reset-button or simply turn it off and on quickly, it will not boot. It only sounds long beeps repeatedly, but nothing else.

However, if I turn the computer off and let it "rest" for a minute, It'll boot just fine.

I can think of two things that could cause these symptoms. One is heat. Something needed in the boot-process is too hot, and it need time to cool off. (notice that whatever it is that gets hot doesnt in any way interfere when the computer is already running and being used.)

The other thing is if a capacitor or something keeps a charge over a curciut that needs to be fully resetted for booting. Giving it some time to empty it's charge would set the state of the curciut back.

I don't even know if it is the motherboard or the PSU (Morex 80W from mini-itx.com) that is causing problems.

Do you have any idea of what I should do next?

(things already done: tried removing all the perhipheral hardware, then putting it back. tried different hardware/cables. tried different RAM modules. ran RAM through MemDoc testing, passed.)

I will try to do a very quick on/off/on to see if I can turn it off before whatever component is causing troubles get too hot. Then turning it back on again. If it is a heat problem, there should be no problems booting.

Also, I have noticed a buzzing sound from the Morex powerbrick. The powerbrick is (as powerbricks tend to be ^_^) passively cooled, and shouldn't really make any noise at all, ne? Might that be a cause of my problems? I just don't see how it could cause these problems with the motherboard.