the problem you are having is with the 16.12 catalyst. You cannot use it with modded bios unless you make some other changes. Also uninstalling it does no good either. The fastest and easiest way to get rid of the problem is to do a fresh install and stay away from 16.12 unless you are well versed in drivers and bios modding. Once you install 16.12 it will behave like 16.12 even if DDU is used. You can do some other mods but for mining it would just be easier to use 16.11 or earlier
Could've also been a bad bios that was flashed, or a psu dropping voltage if its not booting. Probably b est bet is to try to use old drivers instead of worrying about new drivers right now, would be better to use the stock bioses and make sure everything works, then flash if needed then