Try the USB device in different ports. My -70K seems to change which ports it reads during POST with every BIOS update. Sometimes its a USB2, sometimes it's a back panel USB3, sometimes it's a front panel USB3. I have only a USB keyboard and mouse, so just to get into setup I have to play wack-a-mole on the ports after an update until I find the ones that work.
Ended up trying the additional 3.0 slots. on the non integrated controller, and those seemed to work in bios 039. Also I removed the bios battery for about 3.5 hours while watching football, this seemed to clear whatever was stuck with the graphics in the BIOS, and allowed me to flash the BIOS.