One of my contributors cannot access the "add image" screen in "add media". They get the error: you do not have permission to upload files. They don't want to upload files, they want to drop their own url into the "source" field.
I logged in as them and confirm that error. It works fine for me under my own log-in.
I am on wp 2.6.2, my site is http://watchmecreate.com
I have been using Firefox.