Exactly.

The CTD that you always reproduce no matter how much you change or do differrently, you simply cannot get around it. The result, of course, is that you are "blocked" and you can go no further in your campaign. It could be a persitent CTD, but then a persistent might just simply be a verifiable and reproducable CTD. For example, some people have reported that having a spy enter a city consistently causes a CTD, and since it happens every time it is "persistent". Well, if the player chooses not to enter that city with a spy, then the player can skip the CTD and is not "blocked".