I have the same problem but luckily for me my city will save. But it does me no good as my city also has a bug where a number of buildings I've tried to demolish are stuck with the red status bars showing they are in the process of being demolished...but it's permanently stuck, meaning I have no benefits from the buildings, AND I can't use that space anymore.
I really think Cities XL has a huge amount of potential but the fact that they released this game with SO many issues is simple sloppy. That is my biggest complaint.
