Crickey, in all my time messing with True Ambience (a lot) I have never seen that render effect/error.

Can you take out the model (delete from scene) and replace it with a Bryce sphere with the same texture - then render again? That should tell us if this is something induced by the model or inherent to your Bryce setup.

Which version are you running?

Thanks for the info, Len. I'd guessed it was something like that but had never followed the hunch with research.