I find myself in a bit of a problem too. I was hit by this bug before the expansion. What hapened was the Elder Scroll I took from ruins disappeared. Suddenly I couldn't do those quests that needed it. I did the other quests instead. When I updated to the patch 1.6(? The one with the kill cam) I used the console to get the Elder Scroll (00002D513) and my other quests continued . The name of the scroll was simply Elder Scroll.

After updating to Dawnguard the scroll was named Elder Scroll (Dragon). I proceeded to do the Vampire Lord quests. Upon completing the quest in the Soul Cairn, I notice that I was stuck. The first part of the mission (Blood) was done. I had the Elder Scroll (Dragon) in my inventory (I could drop it and sell it. I didn't get the conversation in the Arcaenum.)

Also used help "Elder Scroll (Dragon)" in the console to get another code, but still nothing.

EDIT: Just used console to get passed it :|

setobjectivecompleted DLC1VQElder 10 1

setstage DLC1VQElder 20

Hopefully I don't get a problem when I used the scroll on the Time Wound.