Sam Sartor

Endstone may also be affected

May or may not be intentional, this certainly seems strange however.

This is a culling/normals problem.

This is to be expected and is normal and unavoidable. The world generation was changed in 1.7 so any chunks from before 1.7 will not line up with chunks from 1.7 or later. This is not a bug, simply the new world gen disagreeing with the old.

Obsidian blocks generated by the world also have a missing texture, and, like the ice, obsidian placed by the player renders normally.

Some demonstrations similar bugs:
http://www.youtube.com/watch?v=g5hZtUlrlmo

Please fix this, it has made redstone contraptions and logic difficult.