Direct IP "Out of sync" error

The error message I got was:
OUT OF SYNC! MY SYNC SEED = -185980544 : MY OPTIONS SEED = 0

My friend and I were playing as a team, and we were definitely out of sync; I couldn't see a second city that he had built, and it reported that he got Buddhism to me while he said another civ had gotten it.

Any suggestions?

Maybe one of you edited your ini file to change the synch speed from default 0 to a different number?

There are two seed lines in the ini file one for map generation and one for multiplayer synch

No...but we left the game alone while it loaded and had no problems. So I dunno.