hey i'd like to think ive given some good words too!
the only thing that i am thinking is that maybe one of the objects isn't a full face, or when it is making it the boolean is to complex for it to handle.
This is why i never boolean, it often creates more verts than if i were to take the object that i am making, then create an outline of the object i am looking to have go thru it, then create faces between the two.