So I have been working on recreating stampy's lovely world for the past few months or so. I log on this morning and Minecraft is stuck on the menu screen with no GUI or anything, just the background. I close it down and reopen it. This time it works. I load up the world but find that THE HOUSE HAS BEEN SPLIT IN HALF BY A GAP INTO THE VOID AND A MOUNTAIN THAT I HAD DESTROYED RE-APPEARING. Please fix this issue, it happens too much on my PC. It destroys so much progress that I make and I don't know how to fix it.