Can’t Auto-Update, but permissions are good?

If you’re pretty sure about that the file owner of wordpress folder is as same as that one who runs apache. (use ps aux|grep 'httpd' or ps aux|grep 'apache')

Here is a lousy solution for you:

function force_use_direct_fs($method,$args){
         if($method != 'direct')
              $method = 'direct';
         return $method;
}

add_filter('filesystem_method','force_use_direct_fs',10,2);

Why Would WordPress Request FTP Credentials

wp-admin/includes/file.php

In function get_filesystem_method WordPress will determine the proper filesystem method by comparing the file owner of a temporary file to the user who runs the web server.

Here is the code:

if( getmyuid() == @fileowner($temp_file_name) )
       $method = 'direct';

That’s why I still think the cause is the wrong file owner permission.