Does this perhaps explain why I have this problem ?.
If I go into the map editor and view the 2d map, then take a screenshot picture, then exit WITHOUT saving I get the problems mentioned.
If I do the same thing and exit with a save, then all is ok.
If I made no changes to the map (all I do is take a screenprint) why should the file need to be saved ?.....anyway, it looks like this is the explanation.