Tim.
I only had the USA general data file installed, but I was zooming in over the UK, Anywhere caused the fault.
I have reinstalled the USA general data and the fault reappears wherever you try to zoom.
It happens at the zoom level where the distance scale bar in the bottom left of the screen is on 20 and changes for the third time.
I can reproduce the fault at will by reinstalling the USA general data.
The other data files I have installed are:
BeNeLux
France
Germany
Sweden.
Hugh