To be honest on two counts - firstly, I don't know if a new game would be needed, but suspect it would. Secondly, having looked at the logs, there's nothing I can personally see that would explain what happened. I'm really sorry.
Edit: another attempt, another crash - this time fairly certain it was triggered specifically by sending a trade route to Sidon, which completed their quest for me, which would've granted me suzerainty.
Before launching this game, I did disable the UI mod I'd had enabled this morning, but alas.