Hi Mangatom. Thank you for your feedback. Can you tell me exactly what you did in what order so I can reproduce and fix this? Thank you!
This happens for me too, on Ambermoon.net for Windows 8, 10, 11 (64bit). It seems to happen when trying to start a new game in Ambermoon Advanced 0.0.1, when the previous game was also in Ambermoon Advanced 0.0.1. Starting a new game in Ambermoon Original 1.12 still works, or deleting the ambermoon.cfg file also allows a new game to be started in Ambermoon Advanced 0.0.1.
When the previous game was in Ambermoon Original 1.12, I can start a new game in Ambermoon Advanced 0.0.1. I compared the ambermoon.cfg files depending on which version was previously played, and it looks like the only difference is "GameVersionIndex": 3 for 0.0.1 vs. "GameVersionIndex": 1 for 1.12, everything else is identical.