Tried your Nano BIOS right now at my MSI, the conservative 100/100 version.
Flashed, reboot -> Game over. No screen, no windows, 100% fan speed, thats all.
Flashed back the org. ROM after using dual BIOS switch at card, fortunately it runs again now.
So "thanks" for the fright and 1/2 hour wasted mining time.
![Angry](https://bitcointalk.org/Smileys/default/angry.gif)
I had similar problem on one of my sapphire cards. I flashed the -200mV one. I had to use the bios switch and flash the -150 mV ROM. It works well now.