Hi all,
As I have found a solution for this problem I would like to share with you all.
If none of the above mentioned help you and the game crashed during an AI's TURN then you probably have the same issue that I am having:
The problem is that at a certain moment in the game an AI player is killing another unit from another AI or taking over a city from another AI.
As it happens sometimes (due to mods or game itself I don't know) this makes a bug which will result in a game crash.
Since the AI player will always do the same after you reload a loaded game the problem always keeps occuring and your game becomes unplayable, pretty frustrating when you try to finish for once a marathon deity game on a huge map...
Solution
1) download the mod In Game Editor (IGE)
2) save your game the 1 turn BEFORE the game always crashes.
3) watch the AI players taking turn and notice which AI player is at play when the game crashes.
4) load the saved game again and open up the IGE mod.
5) change player towards the AI player who was at play when the game crashes (click civilization's icon in green and choose the right AI's civilization).
6a) go to the units and cities tabs and look for cities who are close to being destroyed -> delete those cities.
-> change back to your own civilization and continue the game: the bug may be fixed and you can continue your game.
6b) if the above didn't help, you can try to choose EXPLORE or REVEAL ALL on the map through IGE mod and delete all heavilly damaged units from the AI's player or any AI he is fighting with.
6c) if the above didn't help, try looking for any AI player's cities which the crashing AI player is nearly taking over and delete this city.
6d) if all the above didn't help or you don't want to invest time in looking this up, you can choose the option KILL to entirely remove this AI from the game and all his units.
-> this solution should always solve the issue.
6e) if all the above still didn't help then it is most likely that you mistaken the AI player because the game crashing before showing the bugging AI player even takes turn (crashes too fast).
In this case it is a good idea to write down for yourself the turn order of each AI so you can easilly find out which civilization to delete.
So, as you can see there are some sacrifices to be made to the game but hey if the AI player is bugging out your game after 1000+ turns then he DESERVES TO DIE RIGHT??!!!
Don't worry about killing one of the most powerful AI's in this turn, other AI players will gladly take up the empty space especially on deity.
Good luck, hope it helps!