If anyone has any ideas, help appreciated.
Basecamp 4.4.6 (current)
Display map view for any available source from the tree.
Select the Measure Tool.
Click on first point. OK
Click on second point. The 2D map disappears and is replaced by the red X over the whole map view area.
3D view is still OK
Only way to recover the 2D map view is to close, and then reopen, Basecamp.
It only kills the 2D map view for the particular selected source.
If you choose different source from the tree, the 2D map is visible.
Same thing happens if you try to use the measure tool on this map.
Running Win7x64 with current updates.
