CMPSU-650TX No Post after shutdown

I just built my new rig. In short, here's what's happening....

 

It started up fine the first time. I set basic Bios info (system time, device boot order, etc.) and Windows loaded without issue. I can restart the box without any problem. If I do a Windows shutdown, I can start it up again within an hour or two, and everything is fine.

 

***However, if I shutdown and don't power on the box for more than a couple hours, it will not post. Fans spin, and I hear the HDD spin up, but no Post. I have to switch off and back on the PSU before it will post, and at that point I have to go back into Bios and start over as the system time and everything else revert back to defaults.

 

Is this behavior indicative of a defective PSU as I've read elsewhere, or should I be looking at a different component?

 

Thanks in advance!

Yes, I'm testing with a Corsair 620W modular, and I'm getting the same strange behavior. Any suggestions? I've already RMA'ed the motherboard for a different issue, so I'm doubtful I got 2 bad boards in a row. I'm at a loss. I've been messing with this for a month (flash a new version of the bios, try different memory, replace the cpu cooler, replace psu, etc, etc)

 

Thanks for your help.

Turned out to be the motherboard (again). There's something wrong with the PCI-e slots. It works fine with my old PCI video card, but the PCI-e card causes the Bios Amnesia as someone put it on another forum. Hopefully this will help someone else avoid the pain I've had in troubleshooting this thing.