I was making a "tech tree" in single player, planning on moving it to the server when I was done. I had made a few criteria and linked some up. Then out of nowhere, my world closed saying "A Fatal Error Has Occurred, This Connection Has Been Terminated". When I went back into my world, all the criteria were still there. Thinking it was a freak accident, I went back to adding criteria. Then it happened again. When I opened my world yet again, the criteria from before were gone. What is going on?

No clue, the editor in 1.7.10 was very buggy, especially with saving. Hopefully thing will be improved in 1.8.9.