Windows .exe DW20 (1.6.4) - SP World "Gone" after crash

[CFalzone]

Operating System, bit type: Windows 7, x64
Java version/update, bit type: java version "1.6.0_45", x64
Launcher version: v1.3.4
Completed the troubleshooting guide (y/n): n
Logs: https://gist.github.com/cfalzone/8917935
Description of the problem:

Last night my Single play DW20 1.6.4 Map crashed. When I went back in the world does not appear on the "Select World" Screen.

The following error is what happens when I hit the "Select World" Screen:
https://gist.github.com/cfalzone/8917935#file-console-log-L1980

The folder for the world is still there. TIA for your help guys, and hopefully I posted in the right place/format.

 

[lavarthan]

Known bug, but currently no known permanent solution or cause that I'm aware of. Try this for a fix.

 

[CFalzone]

Thanks, that got me going again. If there is anything I could do that would help the community figure out what is causing the issue let me know. I took a backup of the save files before I switched the levels.dat