Thanks for trying. The fix does not work when I leave the level.dat files in.

Thanks for your help! My file had 64 level.dat files (level.dat63 etc). I deleted all but the most recent and renamed it level.dat (since they were numbered 0-63 with none just "level.dat"). I get the following error. Any advice?

My oldest game save still has the rocket silo GUI button at the top left of the screen. Interacting with it causes the game to crash to main menu. Launching a rocket also causes the crash. The save is still playable as long as you don't interact with the top left GUI or launch the rocket. Destroying...