Problem with Vray domelight

[tricky]

I have a very large scene - this is just the (realtively simple) landscape geometry as seen through fly-over camera.

I have been playing around with the dome light as I feel it would be ideal for my external animation - I don't want to use GI, but the ambient occlusion of a vray domelight and the area shadows of a direct sunlight. However, with the domelight, certain areas of the landscape do not render. Even in this case where I have put a vray material override map on everything.

Any suggestions?

[tricky]

Just seemed to have solved this. It appears that the areas of missing render are where there is duplicate geometry! Maybe this should be moved over to the Tips n Tricks forum as "a handy way to find that pesky duplicate geometry"!