It shouldn't be necessary. C2 saves the state of the UI (dialog sizes and positions amongst other things) in the registry. Sometimes new builds change the UI - adding or removing controls from a dialog, and so on. This can make the old saved registry data invalid. It still tries to load it, though, and as a result it gets interpreted as corrupt data. Like you found, it can end up with dialogs not appearing.
Usually I remember to put a note in the changelog stating that you need to clear the registry when I make such changes - I must've forgotten.