Hi eduarcor, are you coming from a poly modeling background? Unlike poly modeling you can't generally move around points and edges of NURBS objects because of how things work with trim curves on an "underlying surface". There is some additional description of this here:
http://moi3d.com/faq#Q:_Why_does_show_points_work_for_some_objects_but_not_others.3F

In NURBS modeling you generally construct things from 2D profile curves, using some to build base shapes and others to cut things with boolean operations. You don't do it by moving around points on the 3D shape like you would in poly modeling.

There are some tips here for people coming from a poly modeling background, they may be helpful:
http://moi3d.com/forum/index.php?webtag=MOI&msg=4865.2

- Michael