I emailed Sun a month ago about this. Prometric told me that they weren't going to fix the drag and drop "feature" (they told me it wasn't a bug) as they'd specifically designed it to function that way.
In K&B's sample self-test questions, some D&D questions involve leaving drop areas blank. Some also admit multiple possible correct answers. Most -- actually all, I think -- involve more choices than blanks. However, I don't know if this applies to the real exam; any veteran care to share?