Hi David... There is a difference between curves and "surface edges"... To select a surface edge you need to do a "drill down" pick, which is as you describe, selecting the surface then the second pick will target that surfaces edge.. The same is for the faces of solids or joined surfaces.. Select the object then the face will become selectable.. The edges take precedence, so you may have to zoom a bit on smaller faces to be able to target them...

Hi David, yup Burr has described that well - selecting edges is a bit different than selecting a "standalone" curve. To select an edge you first do one click on it to select the "whole object" and then a second click will drill in to select either edge or face sub-objects.

That gives you a method to control selecting either an entire solid (with just the first click) or also going in and selecting sub-object pieces with the secondary clicks.

Check out here for some description of how selection works:
http://moi3d.com/2.0/docs/moi_introduction.htm#selection

- Michael