Well, this has been an interesting morning. Michael and I decided to try a game of Civ IV, and immediately on connection, we got "Out of Synch" errors. We are both using Windows, so it's not the dreaded Windows to Mac issue. No, it's the recent 313 patch. A quick round with Google turned up this thread, so we turned off random events. That did the trick. So now, I guess we wait for the next patch. Given how quick this one popped up in MP play, I'm surprised it wasn't caught in testing.