not just configration.php , even just click and look it will change file permission automatically . but also others file like language.php.
I go to check the language manager / chinese tranditional.php just check it . it occurs error.
Fatal error: require_once() [function.require]: Failed opening required '/home/httpd/vhosts/regi168.com/httpdocs/language/chinese_traditional/chinese_traditional.php' (include_path='.:') in /home/httpd/vhosts/regi168.com/httpdocs/includes/Core/loader.php on line 78
I must use ftp to change it back to 644.