I've just updated my game from the latest stable version to the newest svn and all of a sudden my civ is crippled by stupidity. 545 turns in and my size 19 capital city with all education buildings constructed (library and math academy are the most advanced) and it's still at -25. There's literally nothing more I can do about it, yet every turn my research gets longer and longer because of the negative education values in all my cities. When I updated, their values were all in the hundreds. So it seems like there must be something problematic with how much population affects your education rate.