Screen doesn't turn back on sometimes after leaving on overnight

I've had this happen now with my last 2 custom built PCs. I'll leave my computer on overnight and when I return to it in the morning, my monitor is black from being turned off, but won't wake up when I move the mouse or use the keyboard even though they have power (as indicated by their glowing lights). The only common hardware components are the video card, PSU, and DVD drive. My current machine is:

Win 7 Ultimate x64, latest service pack
Gigabyte z97x-ud5h mobo
Intel i4790K
ATI Radeon HD 7970

My previous machine was:
same os (same disk even)
Asus Crosshair v Formula-z
AMD FX-8350
same video card

I do not have any power saving features enabled. My monitor is set to turn off after 15m, but in the advanced power settings I have turned off all sleep and hibernate features. If I walk away for an hour or so, even though the monitor is off, it will wake back up when I move the mouse/keyboard. It seems to only be after I leave it on overnight. The only other common denominator I can think of is that I use Acronis to run a back up on my system around 5am, although it's rather short as it's just doing a diff.

Again, all power save features are off (or should be at least) so I'm not sure what would be causing this, especially given the rather different hardware. I'm wondering if it's the video card at this point? But then why would it only be causing issues after being on overnight?

but in the advanced power settings I have turned off all sleep and hibernate features

I had that problem until I determined I also had to set the Hard Disk to Never shut down in the Advanced settings, apparently keeps Windows from losing track of itself.

Ya, I have that set as well. Hmmm. I wonder if it could be the monitor itself?

Possible, I remember one that needed the power cord unplugged then plugged back in before the display appeared. Have also see where the power cord didn't get fully seated in the monitor and caused problems.