single player bug

*What I expected to happen was...: that i just could play minecraft without the game corrupting itself.

*What actually happened was...: my world saved itself and brought me to the main menu. it said: disconnected by server: connection lost. and i was just playing on singleplayer. so i dont get it.

Steps to Reproduce:
1. you cant trigger it. it happens one of the ten times im playing. its annoying!
2. its the same by my friends!
3. ...