When using the profile options to set the version of Minecraft to be used, downgrading from the snapshot 14w21b back down to released version 1.7.9 causes inventory to be deleted and may cause deletion of items in containers as far away as 500 blocks from the loading point.

What I expected to happen was...:
To downgrade from the snapshot 14w21b, back down to release version 1.7.9, and play the game without loosing my inventory and container items.

What actually happened was...:
After loading, my inventory was empty as well as every container within 500 blocks of me; the emptied containers included chests, furnaces, and even my horse's saddle.

Steps to Reproduce:
1. Play a map in snapshot 14w21b, filling chests and containers.
2. Quit the game and restart the Minecraft Launcher
3. Change profile settings to play in version 1.7.9
4. When loading the map which was previously played in snapshot 14w21b, the character inventory will be gone.

Note: When I attempted to re-create this bug, container items didn't always disappear; however, the inventory was always lost.