Black screen on Selecting single player

I don't know if this affects 13w07a, but it does on 13w07b, which the bug reporter won't allow me to list. Anyway, I tried to load up 13w07b after downloading it from mojang. the first time, I got a black screen on loading in. I deleted and redownloaded the whole bin file, then inserted the snapshot, which got me to the welcome screen. However, when I tried to go to the singleplayer world selection, the game black screened repeatedly until I obfuscated the name of my saves folder