BioWare's removed Dragon Age: Origins DLC Return to Ostagar from Live, thanks to a related title update stopping specialised classes stopped working in the original game.
The update was a precursor to the DLC's release yesterday.
Said the company on the game's forums:
This morning a title update on the Xbox 360 for Dragon Age: Origins was made available in preparation for the release of Return to Ostagar. This title update introduced a previously undetected issue that causes specialization classes to not work correctly in Dragon Age: Origins. We are removing Return to Ostagar from Xbox Live until the issue is resolved and are recommending that you do not download the title update. If you have already performed the update, we apologize for this and are working hard to ensure a fix is available as soon as possible.
The content is to cost $4.99/£3.99 on PSN, 400 BioWare Points on PC and 400 MS Points on 360.
Eventually. Get more detail on what's actually included here.