by Luke Gerhardt.
I'm having this same issue on a new Moodle server running 2.9. I've enabled all the same things, followed all the steps you listed as well, and also the recommendation by Leo.
Has anything worked for you? Is there something new that must be done under 2.9 to make this work?
All my testing so far has been done with Moodle's internal web service test client, FWIW.