Nothing showing on map

I have been using Basecamp for my BMW Navman V unit for several years now.

I had to update my computer recently, and downloaded Basecamp onto the new computer.

Only the Global map would show, so I re-purchased the City Navigator Australia & New Zealand detailed map ($A189.00!!!) and  downloaded it (again) onto my Navman's SD card.  There was no option to download it onto the computer itself.

I know that I will have to have my Navman connected to the computer to be able to display the detailed map, and when I do so I can see that Basecamp selects that map as the one to use.

The problem that I have is that I have very little of the map displaying.  I shows a piecemeal bit of detail here and there on the map, which disappears or appears elsewhere when I zoom in or out.

I've let the unit sit for a considerable time hoping that the issue may be a simple downloading time issue, but nothing happens.

Any suggestions?