Do what Dave suggests. Make the surface live and then draw a new clean poly surface on top. All NURB's surfaces must be quads so upon conversion from subd to NURBs you are going to get multiple quad patches.

Both Subd's and NURBs are poorly implemented in Maya and have not been touched for YEARS. They were clearly a marketing stunt so that they could say Maya supports all they modeling types in the brochures.

You can already see autodesk is stealthily trying to remove subd's and if they do not fix NURBs I am guessing they will be next to go.