The Nether and The End generating random blocks clientside in multiplayer

When entering the Nether in the snapshot, the nether looked weird. The world didn't load good and you could see though the walls. Also I saw a lot of huge blocks made by all kind of different items. It kinda looks like the SkyGrid what Sethbling made. It just spawned on random places in the nether with all kinds of blocks and items.

Server got resetten to 1.4.5, so I wasnt able make a screenshot.