Ok, so I'm some way into the quest line and i got the "Awakening" achievement earlier on. Now when I look it says that i still haven't got it even though I'm further into the quest line and have other achievements. Is this a common issue and does any one know if I'll be able to earn it again on my second play through? Thanks in advance.

The Dawnguard support section has a fix.
http://www.gamesas.com/forum/198-xbox-360-hardware-and-software-support/

Ok thanks for the help, luckily i will only need to redo one achievement so I'll just recover my account when I start my VL play through