3d Paint Tool (3)

I get this msg when I use the "3d paint tool" : "Warning: Some surfaces have no file texture assigned to the current attribute.". If I press the "assign/edit texture button" is like the computer is working, then I have one half of the objet ( I create this object with "Duplicate special") that disapears like this:

What's wrong?

I found what to do. I just deleted the half side that is shadowed and made a duplicate especial from the other side. In this way is working. Probably I forgot something.