Its almost like a pattern, Im playing minecraft one day and i save and quit and it works, now the next time i play, I play for about 2 hours and 30 seconds, and when i try to save and quit i get stuck on  a saving screen and i left it there for 10 minutes, and its stuck on it so i close minecraft and open it again, i see the world picture was when it was last saved, but i load it up and it loads from the last save which would be yesterdays save.