You must convert the nurbs surface to a mesh in Blender for the UV mapping to work properly. Use “ALT+C” to convert to a mesh. Sometimes Blender will keep the original nurbs surface there, (it will say in the pop-up window “convert to mesh - keep original”), so just make sure you delete the nurbs surface and not the mesh one that was created.
Now, on another note, you can UV texture a poly mesh with sub-surf on, it is a little harder to get it to fit properly, but it does work.
Just remember, if you are going to UV texture, then always convert to mesh and you will have no problems.