I entered in my survival world in the snapshot 14w21b and all works correct. And when I change the version in the launcher back to 1.7.9, all the items on the chests, in my inventory and all the item frames desapeared, and the item frames have falled to the ground because all the item frames apeared rotated 90 degrees. And when the game actualize the state of the item frame and say hey i'm hung in the air, then become intem frame entities in the ground.

This happened to me also when in one of the lasts snapshots (sorry I'dont remember which one, maybe 14w17a), when I back from the end the same thing happened.