I have no idea at the moment, as have not seen anything quite like the globe there (and the artefacts on it). For walls, make sure they have thickness. I do suspect geometry more than anything right now, but really without having the scene to look at, would be hard to say (let's see if anyone else has seen anything similar and can say "Oh that's when..."). BTW, why 1.6? Lots of goodies and improvements in newer versions :)