I'll second what leonix007 said - in my experience it has been the riser that dies first when something goes wrong like that.  

One other thing I always do is leave it unplugged and with the BIOS battery removed for a couple minutes - then when you booted it up, restored the BIOS to the factory defaults and make your tweaks.  I've had this solve issues before in the past, although primarily when I had them on the H81 Pro BTC.