Yeah, updating your BIOS involves wiping the flash memory and then writing back to it. If you lose power during this process, your system will be left entirely useless since that flash memory holds the instructions on how to boot up anything else (such as Windows).
I do NOT recommend it unless you are having hardware problems that a BIOS update might resolve. We had one such problem at the computer shop I work at the other day, where a board was throwing up an error on bootup that we resolved with a BIOS update. That's one of the only times we've ever done BIOS updates even at the computer shop.
- Trip