Yeah, I think hibernation mode is too troublesome and unreliable - I think we will see reliable hibernation when solid state (flash) drives get big enough and cheap enough to replace hard drives.

High end graphics cards run their own BIOS. On a reset or "proper" boot the first POST screen reads the graphics BIOS prior to the motherboard BIOS.

I can only assume that on an unsuccessful attempt the motherboard BIOS beats the graphics BIOS so the computer starts but with no display on the monitor.

Actually, all graphics card, even on-board graphics, run their own BIOS and throw up a splash screen during boot. I think the rest of your theory is spot on.

I'd say it's a 50/50 chance it will boot into Windows or else I need to use the "reset" button.

Hmmm, that's not good. I wonder if it is just a timing problem in the motherboard's BIOS, and a new BIOS version might fix it?

It is never good to just press the reset button, but at least at this point in the boot process, no files on the drive have been opened.