The paths on the gnoll quest were blocked by placeables.
Also, the quest makes a tremendous amount of lag!
This has happened to me twice now, perhaps the random terrain generator needs adjusting slightly.
I can agree that I've experienced crazy amounts of lag on both times I have done this quest since after the rebuild. I hadn't thought that it might be the quest itself until now though.
I think it's probably the trees, every area i've seen with large amounts of trees has massive jerky lag for me.
Trees in the Lost kids quest cause me some, not much, but some lag as well. I've not quested gnolls though.
Tweaked. Will see if it fixes it.