OK, the pbs I have loading the game are not only mine since a neutral tester (I guess Dogboy can be considered neutral and is quite known around here) could not open them either.
Considering the number of times it has happened recently, after checking other possible causes and having to dismiss them, after having a look at the pbs a save editor can cause, I consider it is a distinct possibility someone is cheating.
I cannot (yet) and don't want to name anybody but this problem appeared in another PBEM where someone has already noted something strange about a special civ... It leads me to believe there is cheating. I am not 100% sure but can easily be.
I am trustful and especially in PBEMs because I don't even see the interest of cheating (well, actually once I did something that was quite close to cheating so there was a very short-term interest but I backed off quickly). Obviously if I can be weak I am not gonna be judgemental about others (provided it stops). If you play to win, cheat against a computer. Cheating in front of humans will not grant a real win anyway.
So I am proposing this. The turn is replayed and the cheater (if there is one) stops editing saves and we forget the whole thing. The cheater (if any) not only cheats on other players but damages the save file to the point the game might not playable anymore. So ff I keep on getting files that are obviously corrupt, I will look into it carefully with the save files I have (stocked all of them since the beginning), the admin password and a save game editor. If there is a cheater I will find it without any "reasonable doubt", his name will be publicized and the game stopped. If there is none, I will present my apologies and try to find another solution (but quite a lot of alternatives have already been tried !).
My first proposition seems more than fair to me. Of course that means cheating must be terminated in all games immediately.