I do not think it is the lack of names (I have about 10 names or so for Rohan and Dunland both in CI). It may be because of the surname, as I seem to remember there was a surname issue for the Roman factions, but that should be easily checked by adding a few more.

I have found that it is best to not delete any names from names.txt (and lookup, if you're working on 1.5?), as that seemed to cause inexplicable CTDs, and was just too much work for no benefit.