NURBS gone squishy

Im using gluNurbs and have made a rational surface by revolving a NURB line, for the revolution 9 control points along the edges of a square have been used, with 11 knots 0,0,0,0.25,0.25,0.5,0.5,0.75,0.75,1,1,1. The wieghtings for the control points are either 1 in the edge middles or sqrt(0.5) at the corners. The problem is the surface appears extremely distorted in the rotated plane, I have tried to alter everything I can think of… please help! Tom.