Fireplace, Studs and Flat Screen TV?

We live in an apartment and want to hang a 32'' flat screen over the fireplace. The problem is the studs/framework. We found two studs (using stud finder) going up along both outside edges of the fireplace, one going horizontally across up near the ceiling and then the stud finder tells us there is something in the middle right where we would like to hang it, but nothing around that spot. In other words, the stud finder is saying there is a solid piece of wood there, but nothing going up to it or away from it in any direction. The apartments were build in the 80's, what is going on here? Suggestions? We would like to have it up due to young children and that is the only place it can go do to the lay out of the apartment.