For anyone who may have downloaded Nested-Categories from the gallery.
When updating this for BE ver 2.5 I noticed a mismatch in the previous package contents, control and widget.
The control part was fine but the package should have included a Category List folder for the widget, I had in fact packaged the newsletter folder instead.
Apologies, slip of the mouse, too much beer (if such a thing is possible) or just plain old age.
This has now been corrected with simplified versions for BE 2.0 and BE 2.5