The command 'drush.php en admin_menu' could not be found. [error]

with --debug

****@****-var/www/drupal$ drush en admin_menu --debug
Drush bootstrap phase : _drush_bootstrap_drupal_root() [0.022 sec]   [bootstrap]
Initialized Drupal 6.15 root directory at /var/www/drupal [0.033 sec]   [notice]
Drush bootstrap phase : _drush_bootstrap_drupal_site() [0.035 sec]   [bootstrap]
Initialized Drupal site default at sites/default [0.036 sec]            [notice]
Drush bootstrap phase : _drush_bootstrap_drupal_configuration()      [bootstrap]
[0.038 sec]
Drush bootstrap phase : _drush_bootstrap_drupal_database() [0.045    [bootstrap]
sec]
Successfully connected to the Drupal database. [0.045 sec]           [bootstrap]
Drush bootstrap phase : _drush_bootstrap_drupal_full() [0.052 sec]   [bootstrap]
Drush bootstrap phase : _drush_bootstrap_drupal_login() [0.181 sec]  [bootstrap]
The command 'drush.php en admin_menu' could not be found. [0.183 sec][error]

with --verbose

****@****-laptop:/var/www/drupal$ drush en admin_menu --verbose
Initialized Drupal 6.15 root directory at /var/www/drupal               [notice]
Initialized Drupal site default at sites/default                        [notice]
The command 'drush.php en admin_menu' could not be found.            [error]

No body?

When I found the this comment (http://groups.drupal.org/aegir/0.2#comment-80457) i realized that its permission issue.

I moved the drush from /opt to ~/ (home) and i used the head version instead the 2.1 and it solved.