Bad or missing property 'Mapname'

[AntonyVW 62]

Ive posted this before as part of several issues but I think I have a clue as to whats wrong even if I have no idea how to solve the issue.

My problem is that when I press the letter 'M' to get the map and compass up - my map is grey with no actual map being displayed. Howeve as I look at the server info I have just noticed that it carries an error message:

'OpenMap' : bad or missing property 'Mapname'

Anyone any suggestions as to where to locate the problem and how to correct it please? On a 1x1 server I don't get the error, but when I move it to a 2x2 or above I do.

Any help will be gratefully received.