Warning: require_once(//libraries/loader.php) [function.require-once]: failed to open stream: No such file or directory in /libraries/joomla/import.php on line 21

Fatal error: require_once() [function.require]: Failed opening required '//libraries/loader.php' (include_path='.:/:/usr/local/php/pear5') in /libraries/joomla/import.php on line 21