On WP 3.3.1:
1. Create a new post type
2. Create a new field Type (more fields)
3. Add a WYSIWYG field to the type and add it to the post type
4. Remove the default editor from the post type
5. Try adding a new entry to the newly created type.
6. WYSIWYG won't work anymore
7. Edit custom post type and add default editor back in
8. Now WYSIWYG will show up
My get is that something is not loading (js) when the default editor is removed.