While in a world (Customized world type, "Mountain Madness" preset), a large cluster of chunks failed to appear. All interaction with blocks was possible, including breaking and placing, but they appeared invisible. Despite the lack of block rendering, entities still rendered inside of the area. I first encountered the bug when mining below the surface, and later again while flying above it.

I haven't tested to determine if the bug occurs in earlier versions as well, although I haven't encountered it before, which naturally suggests it doesn't. It's possible that it occurs in 14w27a, as I never used that snapshot.