I have a map with 300 plus buildings that has been going for 7 months... I loaded into the beta version, and reverted back because betas are awful & buggy. The map had disappeared from regular 1.2.11, and was only playable in beta. However, though it and it's copies dont show up in the menu in .11, they appear in the 'storage' section. It is a healthy map, not corrupted, and I'm unsure of a fix for it, and don't want to wait for the beta to become a full release, as the last time I did that it erased my old map.