That is odd that both the 12v and 110v systems would be affected isn't it? It would make me think the fault had to be somewhere at, or inline, of the main bus. Any possibility that the main breaker (while reset) has gone bad? I know it's not supposed to be able to reset if it is faulty, but I've seen them do it anyway because the internals were fried.
I'm supposing that you do have house batteries?
If not there I would be tracing my power lines feeding into the main bus backward. Don't know how many times I've found hidden fuses in my rig. Every time I think I know where they all are, I find another one.