Navisworks gets stuck in Select mode

Several times this has happened to me, where Navisworks will get stuck in "selection mode" which prevents me from selecting any of the viewing functions from the Navigation bar. I recently was teaching a class, where several folks in the class had the same problem. I have tried several actions to clear the problem and have found the most reliable: right-click in the background and select SCENE. Seems to clear the problem everytime.