I also ran into the issue of continuous restarts after a Windows based flash update. I think the issue is related to XMP-1600 memory mode, as I repeated the procedure with memory in 1333 mode and it went fine!
So... some words of wisdom (althought I'm sure if you're reading this then it's too late):
A) Do not under any circumstances attempt a Windows-based BIOS update on any Intel 77 board. Use BIOS F7 method which is a LOT safer.
B) Prior to flashing, move memory sticks to bank 0 (black slots) and disable XMP-1600 mode.
Anyway, I was able to recover the BIOS with the following steps:
1. Download a latest BIOS as a .BIO file
2. Put it on a freshly formatted blank USB stick (I used FAT16 on a 2GB stick)
3. Stick it into the leftmost blue USB slot in the back
4. Remove all PCI(e) cards, disconnect all SATA drives
5. Disconnect all peripherals except the mouse, keyboard and display (plug display into MB)
6. Keep only two memory sticks in the black slots (keep blue slots empty)
7. Physically turn off the PSU (with the switch in the back) and remove the battery for at least 1 minute
8. Remove BIOS config jumper
9. Put the battery back it
10. Switch on PSU power
11. Press the power button
12. The board should stay powered, the USB stick, if it has a power LED, should become powered
13. After a while (30-100 seconds) USB should shut down
14. Wait 1/2 minute and physically turn off the PSU
15. Put the BIOS jumper back in (topmost position)
16. Turn PSU back on
17. The power LED (or the MB green LED) should start flashing
18. A flashing LED means BIOS flash is in progress
19. WARNING: A BIOS flash is a slow process. Especially BIOS recovery flash might take up to 30 minutes 
to complete.
20. If any LED is flashing, let the system sit for at least half an hour.
21. After a while your display should come to life! (make sure it's on 
)
So yes, it IS possible to recover from the flash of death. Good luck!