Everything's Gone

So I was building a minigame, and went to update to 14w26c and all the snow, signs, heads, sticky pistons, everything was gone. (The grass was still there, so was the dirt.) I went back to 14w26b and everything was back. "Phew!" I thought. Then I went to put an item in a chest and all the chest was empty! "NOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO!"