After disconnecting the pc from the mains supply, either by unplugging or by pressing the off switch at the back of the PSU, a problem occurs; once all is back on and plugged in the pc will not boot.
The motherboard light is on but no power to anything else, after approx. 1 hour or so the pc will suddenly turn itself on, from here on the pc behaves perfectly. It's stable under full load, has all the right voltages (according to asus PCprobe) and turns on and off without a hitch. The problem only occurs once the power is fully off.
Sadly replacing the PSU with a spare just to test is out of the question, i would have to purchase a new one so obviously i want to be sure of the problem before I shell out.
From my experience, computer that won't boot and come up after a certain amount of time is because they had a small short or something like that and some protection kicked it.
Example: me plugging an optical while pc is running and I thought it was off. Pc goes off instantly, wont boot for 15 mins, me panics, come back online, everything is good.
I don't know how you could know for sure, but I would make sure metal piece, screws or whatever are stuck between the motherboard and the mobo tray, also make sure all the connection are tight. I would think the PSU is defective in some way and trying to protect itself...