I have a similar problem with my mobo GA-EP45-UD3. "Windows 7 Upgrade Advisor Beta" says that "gigabyte GGB36X controller JMicron Tech" should be updated, so first I downloaded from Jmicron site the driver and tried to install it from USB stick, but the Win7 installation said, that it was not compatible. Now I have downloaded a similar driver from http://www.gigabyte.com.tw/,
a driver for gigabyte GGB36X. The file is "motherboard_driver_sata_gb_sata2raid_ep45.exe".
If it works I will know in 15 minutes, but maybe this info is useful to you.