Can not delete sublevel which failed to load.

Sean, I can not say how level Temp_Geometry reference level Racing_Track.
But try this scenarios.

  1. Create level, which have several sublevels, save it, Close editor and delete one of sublevels.
  2. Create levels which have sublevels, than create level which have that levels with sublevels as sublevels. Then delete some topmost sublevels.

But what I thinks - there is some bug in figuring out what sublevels can be deleted and when that menu item is disabled, in any case editor should allow deleting sublevels (here for some reason I can make level current, but not delete it)