Nothing and something is the correct answer.
My current theory looks to a black hole for answers to this - in a black hole, we basically have a huge mass of stuff that exists and yet doesn't. If space-time is warped around it, then if space time were to be thought of as a balloon, with all matter floating around on the surface, the black hole would exist somewhere inside of that balloon. I would think it's the same concept for a big-bang.
This is just my own idea. Theory suggests that the universe, again imagining it as a balloon, will rip itself apart like the balloon popping, because of expansion beyond its limits. I think the estimate was 30-60bln years, don't remember which. The folks call it 'The big rip'. It's relatively new. So if matter can rip itself to shreds, destroying space-time, then the inverse of that would be the next 'big bang'. Meaning that Einstein would be correct in saying the universe is infinite. Just not in the way we imagined.
This would indicate that what exists before the big bang is actually what exists after the big bang, just space-time warps the dimensionality of it. Then if we can say that a higgs boson does in fact give particles mass, well, I haven't really thought about that part much yet. We have competing ideas - one says matter cannot be created or destroyed, another says it can be created but not destroyed. Who knows where we will get with that - I'm waiting on the scientific announcement....
BTW - these are just my opinions based on studies I've seen..
Also, my answer to your OP would be that we simply don't know yet, because we haven't yet proven physics to that degree. That's why we have the haldron collider (sp?)!