Once again it is another post about bugs only this one is on civ rev. I my self have been having a great experience with it since the new update came out. Unfortunately not for my friend and it is not really an in game bug but it actually is an issue with the GameCenter API. The issue is that his game center achievements never get saved or get reseted.
After doing some searching I actually figured this was a widespread issue but then on the iPod Touch 4th generation which I see as quite accurate as it has not been bothering on my 1st generation iPod Touch (which by the way runs iOS 3.1.3) and on my iPad 2 (which runs iOS 6)
So I think this is bassicly an issue with iOS 6 with the Game Center API