Just a suggestion but perhaps first, determine which Rev. Number your board is (it's usually printed either on the board itself or on the documentation that came with the board).
Then go here
http://www.gigabyte.com/products/product-page.aspx?pid=4150#dl
That link is for Revision 1.0, if your board is 1.1 or 1.2 then select the appropriate link at the top of that page.
Check for a BIOS update, I noticed that one of the more recent ones addresses USB compatibility.
Additionally check your other drivers while there to confirm you are using the latest, especially chipset(s).