As silly as it may seem, pull out the paper tray and check if there are any pieces of paper sticking out or bent into the machine. I am a field rep for HP and when I get that error that is usually the culprit.[/B]
That did the trick for me. After my printer indicated "Pick motor stalled", I contacted HP via their Web site. A tech answered that I had to reinitialize the printer (i.e. unplug it while on, replug it after a few minutes). Since that did not work, I wrote back to the tech, who never answered back, even after a friendly reminder that I was still waiting for another solution.
So after two weeks of not being able to use my printer, I see this post, and lo and behold, there was this piece of photo paper stuck behind the paper tray. Once removed, the printer worked just fine. So thank you so much for this explanation! And thanks HP for all your help (insert sarcasm here).