I can confirm the gathering horses quest will not complete for me. Neither will the one where you hunt down spiders. Both will spawn locations, but never progress.
In the case of the horse quest, 2 locations spawn. Moving your champ over one and then the other produces the same result - nothing but the removal of that quest location icon for the horses from the map (but not the quest giver's location). Loading from saves, it doesn't matter which one you clear first, neither will advance the quest.
In the case of the spider quest, two spider locations spawn initially, guarded by spiders. You can clear the spiders and collect silk, that's fine. Once the first one is cleared, the icon for that location is removed, but nothing else happens.After you clear the second spider location, 2 more locations will spawn on the map. For these 2 locations, clearing them just removes the location icon from the map. No new locations are spawned, and the quest cannot be completed.
The bard + dragon quest is bugged. Sometimes it gives you an ability to use on dragons, sometimes it doesn't, choosing the same option (paying 10 Gildar for the song).
Another buggy quest is the one with the Dragon Statues. I haven't worked out where that one is failing, but it cannot be completed. Just stops a couple steps along the way, dont' recall the exact spot, however.
