No clouds, not saving my worlds.

Put the summary of the bug you're having here

What I expected to happen was...:
That I would see clouds- That it WOULD save.

*What actually happened
The clouds had vanished- I lost my sheep farm, my chest with 45 wool, everything.

Steps to Reproduce:
1. (Not saving one) Make something on a 0.6.0 world
2. ...come off it and then go back on.
3. ...everything will be gone.