So i am playing Skyrim in Xbox 360, there is a quest ( Bound until Death) in the dark brotherhood in which you need to kill a woman ( Vittoria Vici ) in a weeding. If you do this quest in Dawnguard it will sometimes glitch the quest Deceiving the herd even if you haven't started it. And basically i can't continue that quest because it got glitch in a part that i gotta put a letter into a body ( Vittoria Vici's body), and i don't have the letter because of the glitch.
I was wondering if someone at Bethesda could fix this glitch as it doesn't allow you to continue the quest. Also if someone knows a fix for this tell me .

I think the body you need to plant the letter on is some guy who works at the meadery in riften. Vittoria has her own quest to be killed by the DB. Using her ,Vittoria for two different missions could be the cause for the glich. I haven't done the DB quests for awhile now, so maybe someone else can varify this.

Yeah the problem is that i didn't even started the quest with the vampires in dawnguard and i got the quest for doing the DB quest. So now i am stuck .