WARNING #1: Pretty fair number of mods installed, but I can't figure out any that would affect this.

Damn. So I've just beaten Jonny-boy in Spellhold, get Saemon to teleport me out, yadda yadda yadda. I get the Horn and go and talk to Saemon in the Vulgar Monkey. So I fade out to cutscene, right?

Nothing that simple.

Instead, I end up teleporting to the other end of the Vulgar Monkey, and a bodiless Desharik telling off Saemon - what an amazing Pirate Lord! Anyways, he delivers his initial lines (before he kills that lady,) and then...nothing. No anything. I've tried going down to his ship - twice - and it hasn't worked. I've worked back from a save prior to first talking to Saemon, and I get the exact same problem.

Is there any way to force the cutscene? According to Infinity Explorer, it's the script called CUT41O that I'm dealing with. If there's anyway to kick it's ass along, that would be good. If that's not doable, how can I end up in the Sahuagin City with the quest in the proper order? (I don't care about the scene really, I just want to be down in SC.) Is there any way to abuse MoveToArea() and not end up without the quest?

First Rule of Bugs: Reload, reload, reload.

You implied that you obtained the Pirate Horn before speaking to Saemon, thus looping the game into a possible bug that BioWare had overlooked. Solution: Reload and collect the Horn after Saemon tells you to do so.

I believe the Sahuagin City is AR2100, but I'm not sure about that.

I recall a thread very similar to this in which I stated that exact thing...

OR, you could just do what you did, and drop the horn on the ground before talking to him.