Thanks for the advice absic, I'll consider doing it the old fashioned way for the next flash if there is to be one!
Matcarfer, it seems I was a bit too hasty in saying I have the exact same board as yours! Mine is actually the GA-770
TA-UD3 listed here:
http://www.gigabyte.com/products/product-page.aspx?pid=3272#ovfor which the F3 bios is the most up to date I can find. We're still experiencing nearly identical issues though. I'll give some more details on what happens with mine:
With EC Firmware set to Hybrid, it does the update and restarts. If this is all I do, the computer boots up just fine. Then when I switch ACC to Auto (or any other option besides Disabled) and save/exit, with F3 Bios windows loads fine but ACC has been automatically switched back to Disabled. With the F2 bios, Windows 7 64-bit was freezing on the Windows loading screen and I had to manually switch ACC back to Disabled to get it to load properly.
This computer is actually for my sister and I'd like to see if I can unlock the extra cores, but at the very least I want to be able to do a decent overclock so I hope this can be resolved for us! Googling around it seems there are a mix of other users who get it work just fine (ACC with EC Firmware set to Hybrid), and others who have the same problem that we are having. Very strange!
I've also inquired to tech support and I'll post it here if/when I hear back.. until then, hopefully some crafty person(s) can help us out