My computer has developed a strange ailment: when I turn it on, the 5V power line from the PSU is very low, hovering at around 4.2V. This is intermittent however, sometimes it jumps back up to 4.98V.
I thought the PSU was dead, but now I'm not so sure. I tested it with a multimeter, under load (a fan), but not connected to the motherboard, and was unable to get it to misbehave. The 5V line is rock steady at 5.02V. I'm inclined at this point to think that the motherboard is leaking current somehow, as I have never found it to be very stable.
The PSU is a Corsair HX520W. The motherboard is a Asus P5K Pro, and the graphics card is a Geforce GTX 285. Everything else has been unplugged from the motherboard, which is resting on the backplate from its box, and is otherwise removed from said box.
Sometimes I can get it running all the way to Linux, or Windows, and there as far as I can tell, putting it under load has no effect on this issue. I recently moved the computer across town, and the problems started when I plugged everything back in again, so is may be something to do with that, although I can't see what, as I had it all properly packed, and so on.
Does anyone have any ideas as to how to proceed? I would like to isolate the component that is causing this, so that I can replace it and be sure of actually curing the problem.
I think I have included all relevant details, but if anyone has any questions, fire away!!