Just as an aside, with Steam you get a 2 hour "play" window to cancel a purchase and request a refund. However in the case of DLC that includes any time spent doing something else in the base game even, as in this case, having the program open to try and get something running.

There certainly seems to be a QA issue here though on behalf of both N3V and Steam, in that a DLC purchase should be complete and install seamlessly from the purchaser's point of view.