Then try to check the following lines in your UNA inc/header.inc.php file:

define('BX_DOL_URL_ROOT', '[my_url]'); ///< site url

define('BX_DIRECTORY_PATH_ROOT', '[my_path]'); ///< site path

Do both constants have the / sign at the end? If not, then try to add it and clear the content of the cache and cache_public folders.