I think Mice and Keyboard should be installed in the USB 2.0 Ports that are just next to the combo PS/2 port. Put your mouse and keyboard in those ports, and then put a USB thumb drive in one of the USB 3.0 ports and see if it boots ok then. Also, all of the USB 3.0 ports at the back of the board are controlled by the ASMedia controller. Did you load the proper ASMedia drivers for them?