From what I can see initally

1. You have different normal directions for your nurbs surfaces, to find out their direction click on the surfaces you wish to join and go to Display -> Nurbs Components -> Normals.
To fix this you need to use Edit Nurbs -> Reverse Surface Direction -> Option Box and choose either U V or both depending on the values of your surface.

2. I'm not sure wheather you know but just in case you don't to join two surfaces you need to have either the same amount of divisions on the surface or at least one side have multiples of two of the other side.

Adam