Steps to reproduce on 6.2.x:
Make sure to test it with HSQL or Postgres. It's not failing on MySQL (way too permissive).
1. Import the roles from the lar attached. (Role admin)
2. Create a site, and active staging with default values.
3. Create a user and assign the created site to it.
4. In the LAR, you will find a permission "userstag", assign this to the created user also.
5. Log in with the user (do not impersonate).
6. Go to the content section of the site.
7. Click on Documents and Media OR Message Boards.
8. Check console for errors.