Same board, same issue. PS is Coolmax ZP-480B. one odd thing that "worked" for one boot, was changing the sata controller of my one sata drive (boot drive) - usb worked after first reboot then promptly failed again after next. could be an irq conflict. have not tried to manually assign. In ubuntu, usb works ootb. clearly a driver problem.
I have read that Gigabyte has had this problem before and is sensitive to the PS. Personally, I think that is seriously lame. Too bad they would design such a great board, rave about their super high qual components, and not be able to deal with such a basic problem. I mean, USB not work? WTF?