Thanks, that explains a lot. Of course, I thought this tut was amazing. Otherwise I wouldn't have spent days and many, many hours trying to figure it out. (That's my lack of Blender experience with a dose of denseness

)
When you say this in the NLA (non-linear animation) editor tab:
In the window that appears, you should see that the Inner Cube (which are our panels) have already been put into the editor.
Are you referring to cube.001? That statement confused me.