My world "Hellville1" keeps freezing and crashing

Put the summary of the bug you're having here

What I expected to happen was...:
To be able to continue mining and playing the game
What actually happened was...
Game lags and then freezes. Black voids down to bedrock appear and have squids spawning and flying out of them. Mined blocks disappear then reappear. Can't fish. Chickens cluck but freeze. Game totally crashes.

Steps to Reproduce:
1. Put a step by step guide on how to trigger the bug here
2. ...It just happens randomly as I play along. Doesn't happen on other worlds, which play just fine. I have made a lot of progress in this world and I dont want to loose it.
3. ..I can usually reset it by quitting (cntr+alt+delete), switching profiles and re-entering it. .