Cannot enable or disable modules in each site created by multisite module

I got some problem a couple of days ago, I post it in the group but no replys, I try this forum this time, help me pls,thx

Hi everybody,
I set up a drupal 5.6 and add the multisite module for creating many sites for my company. as we don't want to deploy the codes again and again for a simple CMS site.

My problem is I cannot enable or disable modules for the created sites.
Should I place the modules in the DIR sites/all/modules or just in the modules directory? --- I tryed this but nothing differents

I followed this guide: http://cvs.drupal.org/viewvc.py/drupal/contributions/modules/multisite_m...
and it seems to works well. what I did just as this:
My server is Debian sarge.
take a look at the virtual host configurations:

debian-testing:/home/zof/drupal# cat /etc/apache2/sites-available/multi-site
NameVirtualHost *
<VirtualHost *>
        ServerAdmin webmaster@localhost
        ServerName ms.nacta.edu.cn
#       AliasMatch ^/site/\w+/(.*) /home/www-data/multi-site/$2
        DocumentRoot /home/www-data/multi-site
        <Directory /home/www-data/multi-site>
                Options Indexes FollowSymLinks MultiViews
                AllowOverride None
                Order allow,deny
                allow from all
        </Directory>

        ErrorLog /var/log/apache2/ms-error.log

        # Possible values include: debug, info, notice, warn, error, crit,
        # alert, emerg.
        LogLevel warn

        CustomLog /var/log/apache2/ms-access.log combined

AliasMatch ^/site/\w+/index.php /home/www-data/multi-site/index.php
AliasMatch ^/site/\w+/(modules|misc|files|themes|sites)/(.*)$ /home/www-data/multi-site/$1/$2
<Location />
    RewriteEngine on
    RewriteCond %{REQUEST_FILENAME} !-f
    RewriteCond %{REQUEST_FILENAME} !-d
    RewriteRule ^home/www-data/multi-site(.*)$ index.php?q=$1 [L,QSA]
  </Location>
 <Location /site>
    RewriteEngine on
    RewriteCond %{REQUEST_URI} ^/site/
    RewriteCond %{REQUEST_URI} !index.php
    RewriteCond %{REQUEST_FILENAME} !-f
    RewriteCond %{REQUEST_FILENAME} !-d
    RewriteRule ^/home/www-data/multi-site/site/(\w+)(/)?(.*)$ http://ms.nacta.edu.cn/site/$1/index.php?q=$3 [L,QSA]
  </Location>

</VirtualHost>

and in the /home/www-data/multi-site/site/default/settings.php add these codes:
1.$cookie_domain = 'ms.nacta.edu.cn';
2.

  $requri = explode('/', request_uri());
  if (sizeof($requri) >1 && $requri[1]=='site' && $requri[2] != '') {
    $my_site_base = $requri[2];
    #this will be the database shared between the main site and the shared sites
    $db_url = 'mysql://root:123456@localhost/ms';
$db_prefix = array(
     'default'   => $my_site_base.'_',
     'access'    => 'main_',
     'filters'   => 'main_',
     'filter_formats' => 'main_',
     'permission' => 'main_',
     'users'     => 'main_',
     'sessions'  => 'main_',
     'role'      => 'main_',
     'authmap'   => 'main_',
     'sequences' => 'main_',
     //'locales_meta' => 'main_',
     //'locales_source' => 'main_',
     //'locales_target' => 'main_'
   );
   $base_url = "http://ms.nacta.edu.cn/site/$my_site_base";
}

It looks fine, I can creat drupal sites without copy the source codes, but when I entered the Administration of the created sites, I found I cannot enable or disable modules, is there anything I missed?
Please help and thanks in advance.