Okay, I did what you suggested, trashed the game (again, including emptying the trash, which included game files after copying them) redownloaded the game, copied the saved game files back over, etc.
Same problem, but I did find something else interesting; talking to Cienna about anything, not necessarily Shanker, seems to trigger it.
Oh, I keep forgetting to clarify, that this is before taking Gladwell's Geas, this time through, so the Geas has nothing to do with it. Apparently. I dunno.
Okay, let me another correction, after dinking with this a little more; it seems to be the pylon, not Cienna. If/when after talking with Shanker or whatever, I take the boat back down to the docks and then overland to the Portal, talk to Cienna, walk back to the boat, etc. everything seems to work fine. If I use the pylon, and then come back, whether or not I talk to anybody, the thing crashes as before.