Mine was the same. No mention that Basecamp should/could be updated but a quick check to Garmin showed the update. I wonder if they pulled the option to auto update when they realised that the new one was causing problems? That way you'd stay which ever version you currently had. Sounds a bit too sensible for Garmin though.
I can't be bothered trying to retrograde it so I'll just not use Basecamp for a bit. If they can sort it within a few months I'll survive!