apart from what was already mentioned, my method is I have a 1GB USB thumb drive that boots up a windows 98 dos shell only, doesn't do anything else. I copy the bios into that and run it from there, It's kinda old school but it still works and much less prone to run into problems.
For you, I recommend using @bios, its their windows version and your board supports it, If you can't get into windows, then you'll have to get into a dos shell..
The simplest method for this is, find a unused USB thumb drive and download DOS USB boot drive from here:
Follow the site instruction..
Once you have the thumb drive ready, you can download the latest bios, it'll include 3 files, a autoexec.bat, a efiflash.exe and z77xd3h.f16 file, copy all of it to the thumb drive root directory, plug it in and boot it up, press F11 or F12 to select the boot menu, select your USB thumb drive and follow the onscreen instruction, DONT turn off your machine during the update process, it may look like it's hanging for a small bit, like 30s to a minute, just let it to its work, it will prompt you when completed..
After bios update and reboot, go into your bios menu and select load optimized or default values, save and shutdown, plug in your 780's and boot, try getting into bios, if you can, then config your bios to the way you had it before.