Started a LAN game with my wife today. Got pretty far through our survival game, lots of resources (diamond armour and weapons, that sort of thing) and managed to build a pretty awesome looking base. I tried to save and quit but the game froze on me. It then showed a crash error on my screen. Worried that our progress for the day was lost due to the crash so I loaded it up again to check out, and I was right... everything we did was lost, roughly 6 hours of building, gathering and fighting monsters to gain XP lost. This has been the 3rd time I believe for this to happen. Only effects LAN play too as I have never had an issue with any of my solo worlds.

Not sure if it is my system giving me trouble or Minecraft itself. If it is the game I hope there would be a fix soon.