If you flashed the bios with the wrong version, the board may not post. Msi's "live update" bios flash utility normally will read your board bios and determine which bios file to use. It's hard to screw it up, but I guess it's possible. You can rma the board back to msi, simply stating that it won't post. No other explanation is necessary. It takes 2-3 weeks to get a replacement board, and I wouldn't try overclocking it again if the current board wasn't working. Overclocking isn't guaranteed; I don't do it anymore. I prefer stability.
I flashed it to the newest version and it was working for 3-4 months without any problems. Recently, it started to refusing to overclock, and that's when I looked into it.