Thanks - I didn't know I could right click to get to those settings - but it brings me to the same place, that's the Change Settings icon (on the Troubleshoot tab) which is greyed out.
Just for info, I'm able to run some other 3D visualization software ok (Vue 5 infinite - Vue 14 trial and Plant Factory).
Would rather get TG working. TGs (even classic TG) skies and surface textures seem much more realistic than I can manage with Vue currently.
S