Thanks so much for the quick replies! I am rendering in MentalRay, but I'll have to get back to you tomorrow about the settings used - I have picked up this project from another intern and he set all the render settings, so I'll have to look them up.

Normals.......ah, I have read about them but really don't understand them. How do I check what direction they are in? I am positive that there is no overlapping geometry - some of the objects that the textures flicker on - including the terrain are based on simple poly plains, so I'm interested to learn more about the normals.

Thanks!