I just encountered a tricky "Acess Denied" error message. After creating a new user, and adding them to a role that has permissions to edit all node types, they were still unable to edit certain nodes. Everything looked fine on the access control settings page. It turns out, they did not have access to the Full HTML Filter, which was used to originally create the nodes. As soon as I granted them permission to the input filter, they were able to edit the nodes.
