I also have world save issues. Today, when I opened Minecraft, a world with a large file size I regularly played on was missing. It was on Beta 1.7.0.2 if that's any help. Another thing I should add is that a short time after buying the game last Christmas, I noticed that there were two worlds that I did not create. One of them had a very small file size with a thumbnail, while the other had no file size and a default thumbnail. Both had no name and had the last played date set to 12/31/1969. The one with the default thumbnail was joinable, and was basically just a new world. The other one was unjoinable.
Matt O.
I also have world save issues. Today, when I opened Minecraft, a world with a large file size I regularly played on was missing. It was on Beta 1.7.0.2 if that's any help. Another thing I should add is that a short time after buying the game last Christmas, I noticed that there were two worlds that I did not create. One of them had a very small file size with a thumbnail, while the other had no file size and a default thumbnail. Both had no name and had the last played date set to 12/31/1969. The one with the default thumbnail was joinable, and was basically just a new world. The other one was unjoinable.