problems with "skinning"

is it possible that I can’t perform “skinning” on NURBS surface curves? Anything I should check for? I’m puzzled because I seem to have followed the tutorial in the blender manual,but it is not working!

They have to be Surfaces (Add >> Surface >> NURBS, not Curve >> NURBS) and they will only skin if all curves have exactly the same number of cv’s.

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