I have got tinyMCE working in the django admin, but all the popups are blank (eg. edit HTML, add image)
The paths to the popup html pages all exist in the right plac
i entered to your answer because i was having the same problem. The first answer helped me to understand the problem but not to fix it.
So...you had your code uploaded to heroku, from where you where trying to open the .js that used the TinyMCE popup, but the staticfiles (so the .js used by the popup) was uploaded to another host (in my case S3).
So i investigated a little and found this solution: https://devcenter.heroku.com/articles/django-assets Which, by the way, worked like a charm, and i had my project already working!
So, basically, what you do with this is to upload your static files along with your code to the same place, so you dont violate the Same Origin Policy.