This is the 1.20 playthrough I have encounter this problem, and imho, it is game breaking, it should be simply fixed ASAP, especially considering all the other threads about it.
In short, the saves the game produces after a specific point in the game become unloadable. The game doesn't CTD when loading but just stays idle with the loading bar stopped at a random percentage (or at least it doesn't crash for at least 5 minutes) after which I simply close the game through the "unresponsive app" window.
I am linking 3 saves, the last one (039.sav) being unloadable. 038.sav is loadable, and what happens after it is I kill the enemy champions next to my sovereign's group, save the game (039.sav) and exit the game. Then I can't load the 039.sav save. I've reproduced it a couple of times. I didn't try saving a couple of turns after 038.sav without killing the enemy unit since it was already 2:30 AM and one should avoid getting frustrated at 02:30 AM.
Random large map, custom sovereign, 8 factions, dense champions, everything else default iirc. I am using these in all my playthroughs.
I link the 037.sav as an earlier save in case you need it, and the debug.err.
https://dl.dropbox.com/u/1385950/037.EleSav
https://dl.dropbox.com/u/1385950/038.EleSav
https://dl.dropbox.com/u/1385950/039.EleSav
https://dl.dropbox.com/u/1385950/debug.err