I cannot finish You Can Depend On Me due to the fact that I do not have a dialog option to do so with Doctor Hildern.... Also as a side note Boone has disappeared on me, no he isnt anywhere in Novac or at the Lucky 38. Just adding my disappointed.

Yeah, I am in the same boat. It is because we finished the Tall Grass mission before doing this quest. From what I can gather, there is no way around it. Worst part is, without completing this quest you can't do other quests. For instance, you can't get Cass as a companion because of it. I am hoping some patch down the road can fix this. The only thing to do is start at a save that you have before Tall Grass (or whatever it's called). I did that mission WAY too long ago so I am going to have to hold out until then. Bugs that keep you from doing quests is more than an irritation for me. Hopefully it will be fixed soon.