Hmmm... Well, if it didn't have issues before, and just developed them for no apparent reason (like updating software or changing/adding hardware) then it's unlikely to be simply the motherboard's revision. As was pointed out above, the simplest thing is to run it without anything, make sure that works, then add parts, one at a time, until it fails. That'll tell you where to look for the problem, but seeing as it's affecting even the early startup, it may be possible you have a corrupted ROM image or setpatch or something...
