I've not personally tried this but I know somebody that has and it's worked for him...

He booted one of the boards with the good BIOS. Then he removed the BIOS chip and replaced it with the bad one whilst it was still running and then reflashed it. Because it was so difficult to get the chips out even with the proper PLCC tool he didn't want to risk it shorting something out so he removed the both chips before starting and only held them in enough for it to make contact. Will take a steady hand and probably an extra one to type with...

Not sure if you'd want to try this as it's not exactly going to be covered under warranty if the magic smoke gets let out. And as I said before, I've never done it personally but my friend did luck out and manage it without anything bad happening.

- Trevor