BSOD with sleep/resume

Continuation of these resume problems.
Last night, I put the system to sleep, tapped space bar twice, and it came back up as it should. Let it go to sleep by itself, today tried to wake it up and no response from the keyboard or mouse (both wireless USB). Hit the reset button, and it starts to boot, but gets stuck after the BIOS/POST screen, blinking cursor. Hit reset again, and it goes through the boot cycle again, only this time I get the Windows flying in logo with "Resuming Windows..." underneath, only to go to a black screen after that, locked. Reset again, with the "resume did not work properly" and had to delete resume data and them it booted normally. I don't see any new mini-dumps, did not get a BSOD either.

How can I find out what caused it to freeze from this? Thanks!

BIOS/POST screen, blinking cursor.

A blinking cursor usually indicates that the BIOS didn't detect the Hard Disk. There is possibly a problem with your HDD or BIOS. Do you have the latest BIOS installed?

Checked BIOS - updated from F6 to F8 version (newest). Works with brief forced sleep, tried once to allow to sleep on its own, appears it woke up without any input (found computer back on later). Will continue to test some more. Any way to find out what input wakes it back up from sleep (even better to make only a certain input from the keyboard wake it up).

Further testing seems to be solved. It has gone through several sleep/wake cycles, on/off cycles and thus far seems ok. I'm going to mark this as solved. Thanks so much for the help!