The game I was playing doesn't work because of some change in format that was just made today with updated beta. That rather stinks.
Of course. New Beta, start new game. It's Always Been That Way.
Your Beta 3 Ideology high-water marks don't even fit into the Beta 4 Ideology grid. Also, costs were changed, and tech Ages were simplified. Map generation was changed, so an old map might not even make sense using the new data structures. It Is Just Not Compatible.
In beta 4, we made some big memory optimizations with FOWExposed and InfluenceMap that helped greatly with performance. I am Sorry about your save game but sadly it may not be cross compatible.