I do not download user content for my own security. Upload to youtube if you need us to view a video or some other hosted service.
I don't know what more to tell you. If you can not edit the field of another user within their profile edit page then you can not ajax edit that field on that users profile. The same applies to editing ones self. This is all basic CB configuration and completely independent of CB Core Fields Ajax. I have confirmed this all works perfectly fine on your own site once configured as I've instructed.