I've made a square nurbs shape that I want to extrude along a cv curve. As the nurbs square are not attached, I've selected the edges and attached them with the Edit Curves > Attach Curves (reset settings to the defaults). This creates a new shape and I attach it the curve in the correct way. When I Extrude to polygons with the correct parameters, general, polygon, quads etc it seems to work but soem of the verticies don't connect on the corners, you can see this if you press 3 to go to high res mode.
Is this a bug ? maybe i'm not connecting the square properly, if i use the same method with a circle it works fine ?

Any ideas ?