The word is that it is related in large part to the threat of the anticipated writer's strike, although it may also have something to do with this season's weaker ratings for Heroes. The show has taken a bit longer this season to pick up steam and finally start moving forward with it's story, with the first few episodes kind of dragging. Having said that, as of this week's episode it does finally seem to be on track.
Regarding Origins, the show may not be totally dead: Depending on how things work out it may just be pushed back to next season. I think it's kind of a bummer, it sounded like a cool concept.