hi, i had the same problem.
Flashing vbios threw ASUS GPU Tweaker and the process break during the installation.
After that i was unable to boot, ********* upgrade!
I solved my problem, i put two graphic cards my new GTX770 (without alim) and my old GTX 660 (with alim) in order to boot on windows.
Then i used this tool for reflash the vbios of the 770 link
here.
Now all is fine and my card run well.
Hope it can help you or other users.