This has to be a glitch as I've had no other problems with the game up until this point. Killing one of the witches at Orphan Rock (typically the 3rd one) during the quest 'The Blessing of Nature' always locks the game up. No matter what I kill her with, spells or weapons, the game instantly freezes. I see no current way of completing this quest for a non-high level stealth character until this is fixed.