So did you free the prisoner or did it never come up?
I did lust for powder after going to Gutgash as well and didn't have any problems. The bug I've heard about is if you complete lust for powder freeing the prisoner (which lets you build the armoury) but you don't actually build the armoury (so the mission is complete but you didn't walk up and build the armoury) and then continue on with the game and when you come back later (apparently) sometimes it won't let you build the armoury even though the mission is complete.
I did lust for powder after going to Gutgash as well and didn't have any problems. The bug I've heard about is if you complete lust for powder freeing the prisoner (which lets you build the armoury) but you don't actually build the armoury (so the mission is complete but you didn't walk up and build the armoury) and then continue on with the game and when you come back later (apparently) sometimes it won't let you build the armoury even though the mission is complete.