Hasta La Motion!

I am gearing up for a new scene + tutorial to go along with it as I am learning about PyroFX. The shot is basically going to be a large explosion that is visible from space and clears out some cloud layers with a blast wave as well as some scorched earth effects. The only problem is, when I try to make my fireball localized for some test shots (I am trying to use a box that is close to the surface for now), nothing happens. Big fat nada. If I use the sphere that I am using for the planetary surface it works, but not the box or grid.

Anyone have any ideas on why this would be?

On a side note, if anyone can direct me to some great fireball tutorials for Houdini, I would love to get some assistance from some other aspects from there.

When I put together the tutorial, I want to do it as a series, so I can get a few other things put together before I need this, but it would be nice to be able to get the explosion looking right.