You might be using custom textures on you shape. If thats the case, youll need to download a program called Wally. Heres the link =
http://www.telefragged.com/wally/Go to that link, click on the link "Downloads" then download the Wally Wad Viewing Program thing.
Now once you get that downloaded, install it. When you open it up, open the location of the .wad you are using for Worldcraft. Open it up, and you'll get a table of textures that are in that .wad. Now choose the textures you used on your shape *.vol* and export them to a .bmp file.
After that, youll need the program Visual VT which i do not have a link for *if you cant find it i can e-mail it to you*
Once you get Visual Vt, open it up. Select the .bmps you got out of the .wad and add them to the .vol list. once you add them, create your .vol.
Now that you have your .vol of textures, insert them into you RegisterUserObjects.cs. Load the game, and add in the textures befor you add in you shape.
If this doesn't work, then i will shoot myself for the waste of time;) But i think this is it.