A couple things:
1) Were you playing a v.72 campaign and then upgraded to v.74? (there is a ports bug which isn't solved when this happens). If you are playing a barand new campaiagn in v.74, then this isn't your problem.
2) Load up the game for the turn before the CTD, and do NOT activate the scripts (when you a click on a city and the advisor box appears, don't click on it). If the game does not CTD, let a turn or two pass before activating the script, and hopefully it will proceed normally.
3) If 1 and 2 don't help, try the "toggle_fow" command (access this screen by using the ~ key. The same key also closes the screen) to reveal the map, and see if the AI is conquering Alexandria on the turn of the CTD. There is a know bug involving the "Alexander's Body" script. If this is the problem, #2 should solve it temporarily until you can conquer Alexandria yourself.
4) If nothing else is working, we have a "neutered trait file" which can be used to test whether traits are causing the CTD. You will have to replace the existing file with this one, and see if that eliminates the CTDs.
Edit: To answer a few of your other questions:
1) Destroyed and partially destroyed "enemy" governments will not cause a CTD. You should demolish them after conquering a city, as they allow for the recruitment of units you really aren't entitled to. This is an exploit.
2) Here are the commands you can add to your desktop shortcut. There may be more, but these are the ones I use:
-nm = No movies (speeds up the launch)
-show_err = Sometimes (but not always) will tell you what caused the game to crash
-ne = Runs the game in "windowed mode" (helps if you are doing other things on the PC)
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