Administration Theme not working when theme selected for virtual site

Set up a workaround.

1. Installed Administration Theme module (http://drupal.org/project/admin_theme).
2. Added the following function to my custom module:
   
   function _needs_admin_theme() {
  $admin_theme_disallow = FALSE;
  $admin_theme = FALSE;
 
  // check if some paths are disallow to get the theme
  if (trim(variable_get('admin_theme_path_disallow', '')) != '') {
    // pages that are defined by their normal path
    $admin_theme_disallow = drupal_match_path($_GET['q'], variable_get('admin_theme_path_disallow', ''));
   
    // pages that are defined with their alias
    $alias = drupal_get_path_alias($_GET['q']);
    if ($alias != $_GET['q']) {
      $admin_theme_disallow = $admin_theme || drupal_match_path($alias, variable_get('admin_theme_path_disallow', ''));
    }
  }
 
  // we should not show the admin theme if the user has no access or the path is in the disallow list
  if (!user_access('access admin theme') || $admin_theme_disallow) {
    global $custom_theme;
    $custom_theme = '0';
    return;
  }
 
  $admin_theme = (arg(0) == 'admin' || (variable_get('node_admin_theme', '0') && arg(0) == 'node' && (arg(1) == 'add' || arg(2) == 'edit')));
  // check if an option is enabled and if it results to TRUE
  $list = admin_theme_list();
  foreach ($list as $info) {
    $var = admin_theme_variable_name($info['module'], $info['option']);
    if ((bool)variable_get($var, '0') && module_invoke($info['module'], 'admin_theme', 'check', $info['option'])) {
      $admin_theme = TRUE;
    }
  }
 
  // some custom defined pages should get admin theme
  if (trim(variable_get('admin_theme_path', '')) != '') {
    // pages that are defined by their normal path
    $admin_theme = $admin_theme || drupal_match_path($_GET['q'], variable_get('admin_theme_path', ''));
   
    // pages that are defined with their alias
    $alias = drupal_get_path_alias($_GET['q']);
    if ($alias != $_GET['q']) {
      $admin_theme = $admin_theme || drupal_match_path($alias, variable_get('admin_theme_path', ''));
    }
  }
 
  // Use the admin theme for the current request (if global admin theme setting is checked).
  return $admin_theme;
}
   This code was adapted from the admin_theme.module and the system_init() hook in system.module
3. Replaced virtual_site_theme.module line 115 with the following:
   if (($context['theme']) && (!_needs_admin_theme())) {

I know this is a bit of a hack, but it accomplishes what I need for the time being.

My solution is:
1) Go to admin/build/sites
2) Don't use 'Theme' feature (set to 'skip this feature') for every virtual site
3) Use 'Variable' feature for every virtual site:
theme_default=zen_subtheme
admin_theme=garland

(zen_subtheme is the name of your default theme and garland is the name of your admin theme)

I've also change weight of module 'Virtual Sites' to -1 in {system} table.