Paint Skin Weights Tool Problem
 

I'm having a problem with the paint weights tool. I select the character mesh, and go into the tool, but none of the joints come up and the mesh doesn't change to greyscale. I have hardware texturing off, (even if it was on the joints would still appear anyway!) and the mesh has the skin cluster on it, it just stopped working for no reason! I don't really want to have to unbind and re-skin the whole thing,(seeing as when I export skin weights, unbind, rebind and import skin weights, moving the IK handles, or the joints of the skeleton makes the skeleton move without the mesh for no discernible reason) so does anybody have a clue what to do here?

PS, I'm using 2009