Minecraft stoped responding while playing around...

While I was getting some wood my game just stoped respondind (did not closed)
I waited it for about 3 minutes and my computer isn't slow,what i mean is that everything was running smooth, even Minecraft was smooth while playing.
I needed to close the window from the X button.
It closed without problems,but when i start it again, minecraft is just running weird,the map wasn't saved,so i did the stuff that where missing again,I re-opened the map and they were GONE AGAIN,I didn't made anything else,just closed the MAP (not the game) and re-opened,the stuff were there again, so I don't really know what happend.
PS:Yes, my java is updated.