I was playing the direwolf20 1.6.4, version 1.0.14, in my world when this happened. It shut down suddenly when I was playing as if it crashed. No crash report, sorry. But when I loaded everything back up, my world that I had been playing in, was gone. I freaked out a little because I had spent a significant amount of time in it. But I thought, mabye something is wrong with the world file, So I will make a new folder with the same name, and put the files, including waypoint data, loaded chunks, etc, into the new folder. Still, the world did not show up. So I got rid of the new world folder, (still had the first one of course) and tried making a new world with the minecraft "world creator". (I really hope whatever I did wrong is not a blatantly obvious way to wreck worlds). Same name, same world generator settings. And once the world was "created" I was in the same place I was in when everything crashed, I had all the same waypoints, morphs and inventories. But when I placed blocks in the world and quit/saved the world, and got back in, I was in the same place I was in before, but the blocks I had placed were gone. From the world and my inventory. Then I tried mining some more blocks just to see what would happen when I saved and re-joined. And sure enough, nothing in the world had changed, same position as when I quit, and the blocks I mined were in my inventory. This has happened to me before, I didn't report it because I thought it was a "rare" bug . The first time it happened was in dw20 1.6.4 version 1.0.12. I don't know if this is something I did wrong and therefore, I should fix it. Or if it is the developers fault. I am inclined to think the former. I could REALLY use some help with figuring this out. Sorry about the long thread, but I felt detail, was a necessity. Also if I need to, I can upload a short video showing what happens.