Very similar issue. I had three cities running together on a PRIVATE region (Cape Trinity). For a while all three were working together nicely. Then one day Norwich Hills stopped processing properly and had to be rolled back or abandoned. I tried rolling it back and each time I did it would tell me I was having a processing error and then tell me to rollback again. I was stuck in an infinite rollback loop. It was quite discouraging. I feel like spending so much money on a game that is so glitchy is extremely disappointing. I will probably not be buying from EA/Maxis in the future despite being a loyal Maxis fan from 1997 on...
