I started Minecraft just now, and it started loading. Then, instead of opening, it loaded again, but this time with a caption on top of the loading screen. (minecraft jars, bugs, ect.)
When it was finished it said Minecraft 1.5.2 instead of 1.5.1, so it apparently updated. Problem is, when I clicked on Single Player, all my maps were gone. I then went to the .minecraft folder, and clicked on Saves. All of my worlds were there. I lanched the game again, but my saved maps weren't showing up.