I read somewhere, I think, that if you load a mod from another language this can break the topic / greeting generation. An NPC says hi but doesn't continue his dialoge or the quest doesn't update. There is supposed to be a fix for this but I don't remember what it was.
Also, scripts can be broken like the ones in forts for opening the gates.

A mod made in another language can do many things but they are mostly related to the mod, to what it exactly does. I installed many english and a few german and french mods on a russian version (they mostly were the only awailable) - and all I got changed are languages of: names of many locations, messages, stock items names and topic names. The topics themselves work and the greetings work. You must have some specific mod that gives you a problem.