Reading http://news.softpedia.com/news/Iranians-Capture-US-Drone-wit... it sounds more like the attack was on the drone itself which manifests itself if the drone loses GPS lock. Perhaps a secondary navigation system that can more easily be spoofed?

Also, this article in New Scientist http://www.newscientist.com/blogs/onepercent/2011/12/did-ira... says that the drone was damaged on landing, hence the drapes around the bottom of the aircraft in the picture.