Culture. Too much right now.
This is with 199 cities each at only ~146,000 culture = ~29 million, which shouldn't be enough to overflow signed integers. Are the numbers scaled or something? Also, research overflow overflowed.
2^15 is 32,768.
And 2^31 is over 2 billion.
The closest powers of 2 to 29 million are 2^24 and 2^25.
Oh, Holy Crap/bOh crap.