In addition to the start up issue, you also have issue with USB and POST. The scenario is different from others.
Please try another PSU first.
If you don't have another PSU, please send the motherboard to our RMA for further examination.
Sounds like you're having the same symptoms described by many others in this thread with the Dark Hero version of this board.
I also have the same exact motherboard and had the same issue, except for me, it happened when I put the PC to sleep - since I hardly every shutdown my PC. I posted my issue in the Dark Hero thread as well. Long story short, I submitted an RMA (near end of last year), they sent me a different board (not sure if it was new or refurb) but the problem hasn't happened since. They never exactly told me what was wrong when I got the replacement sent.
There is obviously an issue with the Cross hair Viii Hero series boards (both dark and non-dark versions) and ASUS needs to just come out and be upfront and properly address this issue instead of giving people the run around.
Hopefully you can get the proper help you deserve and ASUS will actually address this issue.