When going into the 14w26c snapshot, the command blocks loose the commands and blocks disappear.
Put the summary of the bug you're having here
What I expected to happen was: the blocks would be there and the commands in command blocks would have been there.
What actually happened was: There were no blocks in the world and then when I went into previous versions (14w26b) the command blocks had no commands in.
Steps to Reproduce:
1. Make a world in 14w26b (or lower versions) and then place a command block with a command in it.
2. Go into 14w26c and then everything would have gone.
Environment
Windows 7
Linked Issues
Created Issue:
When going into the 14w26c snapshot, the command blocks loose the commands and blocks disappear.
Put the summary of the bug you're having here
What I expected to happen was: the blocks would be there and the commands in command blocks would have been there.
What actually happened was: There were no blocks in the world and then when I went into previous versions (14w26b) the command blocks had no commands in.
Steps to Reproduce:
1. Make a world in 14w26b (or lower versions) and then place a command block with a command in it.
2. Go into 14w26c and then everything would have gone.Environment
Windows 7
duplicates

This does not only duplicate like 100 posts about the issue, it was also posted on the mojang webpage before:
"If you are updating from 14w26a or 14w26b, your saved world has corrupted blocks and it will be heavily damaged once you open it in 14w26c. Please use a world backup that was saved with a pre-14w26 version.
Never use snapshots without first making backups of your saved worlds."
Source: https://mojang.com/2014/06/minecraft-snapshot-14w26a/