Have you installed the ON/OFF drivers ?
"Quote off Gigabyte promo screen"
With a simple On/Off Charge driver update, GIGABYTE motherboard users are able to take full advantage of USB charging of their iPhone/iPad/iPod Touch, giving them more options and convenience when recharging their new device.
* Due to certain mobile phone limitations, users may need to connect the mobile phone to their PC before the PC
enters S4/S5 mode to enable a quick charge from non ON/OFF Charge USB ports.
* Maximum 3 devices can be charged at the same time. Charging current may vary with PSU 5V stand-by spec.
On/Off Charge driver download
When you install the ON/OFF charge driver, please update the latest BIOS version for the best product efficiency.
Aussie Allan.... UPDATE, As far as I know....your PSU must support...... "at least 1Watt of power in it's XX state"