Do you have a USB keyboard? If so, do you have USB keyboard support enabled in the BIOS? You can get by without it inside the actual BIOS itself (i.e., the BIOS can read the kbd), but to use the RAID BIOS, or anything else that you want to do before the OS loads its USB drivers, you need to enable it...
I followed your suggestion--went into BIOS Setup > Integrated Peripherals > USB Keyboard Support, and enabled it.
Tried the F8 key again. No joy.
I've got a support request in to Gigabyte's site; maybe they'll have some ideas.
Also: I brought up the .pdf file for that board's manual, and did a search for "Safe Mode". Not one hit.
It's all good, though. I can access Safe Mode thru msconfig, I guess. It's still a good board [:-)
Have an excellent day!