Converted from an old (Beta) save to version 1.8
On entering the world only the skybox and clouds show but opening and closing the menu seems to resolve this.
However all my chests have completely disappeared meaning I only have the items in my inventory.
Also all nether portals become unlit.

Tried this with several different saves with the same results except in one there was also a problem with doors where only the bottom half of the door was visible and it could not be activated or destroyed.