I put some items in a chest, take some out of a furnace and log out (successfully). Came back few minutes later and the items I put into the chest were gone and the items i took out of the furnace were still in there.

Minecraft didn't crash or anything like that.

Seems like the player data and/or the world data aren't in sync and it doesn't save both of them on logging out. (Player data was correct but world data not)

Really hope this helps.. finger crossing