Hi Lang - it looks like your upper piece is made up of many different faces (and therefore many different edges instead of just one edge) because the curves you used to construct the upper piece were made up of many different sub segments. You can see the different segments by selecting them and using Edit > Separate.

When you construct a surface from a segmented curve, it will generate a bunch of different faces, with one face for each sub segment. In order to avoid that you need to remove the segmentation from your curves and make the curve to be just one single segment instead of many. The easiest way to do that is to run the Rebuild command on it:
http://moi3d.com/2.0/docs/moi_command_reference10.htm#rebuild

Also see this previous thread going over a similar thing with the same tutorial:
http://moi3d.com/forum/index.php?webtag=MOI&msg=5001.1

- Michael