I think I found a problem in xml for the Civname_CIV4CivilizationInfos.xml file. This is with 1.75c.
It doesn't seem to cause any problems if the extra civ starts the game at the beginning. It pops up if you have Barbarian Civs active. I mentioned this on another thread, but I've been checking the files for the civs and they all seem to have this.
Here is an xml tag for InitialCivics from the main file:
Here is what I've been finding in the extra civs' files:
Again: It doesn't seem to cause any problems if you don't use Barbarian Civs. If you do, and one of these additional civs becomes a full-fledged civilization, the game will crash. Possibly with first contact, possibly not. I didn't get far enough into the game to see what happened if a civ on the New World became one w/o any outside contact.
I changed the 9 I'm currently using to be the same as the main file, but that setting is causing an oddity in any civ: the new civ's civic choices are messed up. If they start the game, they start with normal civics, but the new ones don't have banditry as a basic civ for some reason. Going to try adding that in right after barter, since that's how it seems to show up in my worldbuilder saves for starting civs.