Hi guys
I am not sure if this will work .. because I myself always face many problems when I model in NURBS .. so I always find out a way to get my self out of it and proceed the work ..
Here we go.
First delete the history of your surface then (its just a habit), then duplicate it and delete the history for the duplicated surface as well now try to do what you wanted to do
Or one other thing convert it to poly then again to NURBS (not recommended)
Hope these help
Have a nice day every one
Saeed AG
Mr_Flamenco™( the Man Who Summoned By Mankind)