I've successfully updated my BIOS quite a few times. However, the last time I did it the computer just died. It just plain wouldn't start and I couldn't do anything about it.
It was the only time I've had to take the computer to get it repaired. I think the problem has to be overcome by firing up the computer with a known good BIOS chip and then, with the computer running, unplugging it and putting the corrupt one back in. From there the chip can be re-flashed and all will be well again. Does that sound right?
Unless you have the facilities to do something like that there is, as far as I know, no way to get back into the computer to do anything once the BIOS update has gone wrong.
As long as the computer works I won't be updating the BIOS again!
In the repair shop they suspected that the BIOS file I'd used might have had a virus. It hadn't come from the motherboard manufacturers.