This may sound like an odd question but have you tried replaceing the motherboard battery of your P5N32-E with one from your previous motherboard? I ask as sometimes when a board is returned from RMA they come with a dead or dieing battery.
Your symptoms sound similar to when I clear my CMOS the lazy way by removeing the battery, the system powers on and fans move but it doesn't POST until the battery is put back in. I know that you have managed to post once or twice and even get into the BIOS but this could simply mean that the battery is coming to the end of its life.
I know its not much of a suggestion but its quick and simple to do and at least worth a try.