I was looking through my achievements and noticed the last quest achievement i needed was 'Awakening'... i assumed it was a quest unique to the vampire side, however after looking through my completed quests i noticed i HAD already completed awakening, the quest where you free Serana...

I want to know what the [censored] happened... this happened to me with Fallout 3 years ago, it took ALL my broken steel achievements off me, thank god this was only one, and i can just reload to the quest and try and regain it... but the fact that it will be recorded as achieved AFTER all the other dawnguard achievements will piss me off immensely... it will make me feel all out of place xD

Seriously.. dafuq

EDIT: I've only just got it now for reloading and finishing the last bit of quest, but its place on my achievement list is going to haunt me xD

EDIT: Is this happening to everyone? Looking at my friends achievement list, he also does not have awakening despite having completed the DLC :/

Same here, except it says I have 56 of 60 achievements, but when I go to look at them I have 59 done.

This was caused by a glitch when dawnguard first came out. On the main achievement screen, it said () out of 50 achievements. Go and click on skyrim, and at the bottom left it would say () out of 60 achievements. When they fixed it, deleted some achievements.