When I tried to deploy a Task Sequence in CM 2012, I noticed two surprising elements.
One, that the Deploy Task Sequence option was greyed out. I checked almost everything related to the task sequence, but found nothing that could change the status. My colleague Sreekanth had already went through the same pain, and found that the Format and partition disk TS was throwing an error, if you go to the properties of the TS.
To fix the problem, I went to edit the TS and removed the existing Partition disk step and replaced it with a new Format and partition disk TS. Saved the TS and again tried to deploy it. Worked this time!!