Chances are you just need to set the NURBs tesselation so it will render properly.

Change the tool set from modeling to rendering in the drop down box at the top left corner. Then select the NURBs object, and select Render > Set NURBs Tesselation from the top drop down menu. This will do some calculations and even though the object may not look "complete", when you render it will look as the green outline indicates it will look.