Alright, so with a board I have had no issues previously, had a restart and it froze at b4 error code that says USB hot plug according to the handbook.  I tried a CMOS reset multiple times with no result and no boot.  I switched BIOS settings and with both 1 and 2 had it freeze at FF error code which says has not been defined.  Finally I switched back to 3, unplugged all USB devices from the computer and reset and it booted directly back to windows.   I was wondering if anyone had a similar problem or a potential solution for it.
 
Also, I posted a topic a few months ago regarding a problem with the USB devices and the motherboard which I have had yet to be resolved.  I can use the top most USB slots without issue for the most part.  However, if I try to utilize the other USB slots the windows 8 add/remove hardware sounds connecting and disconnecting the devices.  It happens more when attempting to play games.
System Specs:
Windows 8.1 Pro
Intel i7 4820k
Ram: 16 GB
Twin EVGA GTX 760s
1000W EVGA Supernova PSU
3 TB standard HD
256 GB SSD

niowa

I think that one of your USB devices is being recognized as a boot device.. I would suggest that you try setting first that under fast boot (USB disabled  until OS is loaded) and disable all but UEFI windows boot order, if not using UEFI then disable all but your boot drive and note it is possible form windows to boot to bios from the update and recovery option and select advanced tools and go thru the menu until you find boot to firmware/UEFI... you also might try plugging in you USB devices one at ah time until you find the incompatibility. before doing the above their might be a known issue from that devices manufacturer an update for it may be available. and I would still do the above fixed or not....hope that helps         

^  For those people who can't find their reading glasses.