First, I have followed the basic premise from Joe's Rigging 2 CD (add the Bone Deform, add the hips and set te slip to 1, ann a transform null, add spine bones and parent them to the null). I then added the arm and leg (not putting in the muscle bones or setting up IK just yet.
I then added a tail that is parented to the hips.
Going into te animate tab, I select the bones and rotate them in all three axes, and nothing happens. The bones move, but the mesh does not deform.
As I said, I haven't added IK or any expressions or anything yet, so there is not mush that can be going wrong, but something clearly is.