I got the save to move on... and then didn't save it. I gave Viberi (or whatever that northern town is) to Thrace with 2000 gold (from a cancelled market) and it went just fine. I then reloaded to try it with no gold (which works too) and it crashed. I've tried a few more times and can't get it to move on again, but it IS possible.

It's definitely Nicomedia and the other city revolting. When it advanced, the cities both stayed with Rome and did not revolt. It's definitely possible to move this save on though, so just keep loading and trying until it works (I would but I have to go to work). Alternatively, is there a console command to change ownership of the cities?