Rocael,
the only permissions I can find are related to the portal_id (portal_read_portal, portal_edit_portal, portal_admin_portal). If you can move elements on the customize page you must have the edit and/or admin privilege. I don't think you have a permission problem.
I have no experience with developing portlets myself so I'm mostly guessing here. I would probably check the HTML source, maybe add debug statements to the portal::evaluate_element proc or to new-portal/www/render_styles/individual/render-element.tcl. Any error messages in the log file?
