CS problem

#1 That means that your mesh is part of a heirarchy. It needs to be off on its own. It can't be a child of anything.

#2 Adam is right, if the skin is in the heirarchy AND connected to the bones via the skin modifier, it will attempt to export it twice. Thus the bones must be in the heirarchy along with any non-skin meshes, and the skin mesh must be unlinked (like the bounding box)