Cita: FROM "projects" AS pr,"users" AS u,"forums" AS forums
LEFT JOIN "forum_messages" AS l ON l.message_id = forum_last_id
LEFT JOIN "forum_messages" AS c ON c.message_forum = forum_id
LEFT JOIN "forum_watch" AS w ON watch_user = 1 AND watch_forum = forum_id
LEFT JOIN "forum_visits" AS v ON visit_user = 1 AND visit_forum = forum_id and visit_message = c.message_id
LEFT JOIN "contacts" AS cts ON contact_id = u.user_contact
LEFT JOIN "companies" AS co ON co.company_id = pr.project_company
LEFT JOIN "project_departments" AS project_departments ON pr.project_id = project_departments.project_id
LEFT JOIN "departments" AS dep ON dep.dept_id=project_departments.department_id
Primero separas las tablas con coma y luego realizas anidaciones con left join. No entiendo que tratas de hacer con esto.
fijate que el error te lo muestra en la tabla u que corresponde a users que va despues del from a la tabla projects.
Por que no haces todas las tablas con sentencias join?
Esto es un error de sintaxis que postgresql no logra resolver.
saludos