On Gigabyte motherboards it is possible to set a property called "xHCI Mode" in the BIOS. In combination with the property "xHCI Pre-Boot Driver" you can influence the pre-boot behaviour of the USB 3.0 ports. Disabling "xHCI Mode" will turn off USB 3.0 entirely and convert all the ports to USB2.0. For this reason please check whether the "xHCI Mode" is set correctly in the BIOS.
This applies only to the Z77, H77, B75 and Q77 boards with integrated Intel USB 3.0 ports.