We haven't been able to reproduce this issue here, though we know of two people (now) who have experienced it. This week's release might help since the towns database has been replaced.

Think I might have found a little bug. If you plan a route where your waypoints are defined by towns along the way - e.g. plan a trip from East Midlands to Stansted and pick Market Harborough as a waypoint - then save your file. When you later reopen the file Market Harborough reappears in the plan as a lat/long coordinate rather than as 'Market Harborough' The only way to avoid this seems to be to explicitly create your own waypoints with the town names.