[support] Drush problem

[Roger]

I  cd /var/www/html/directory which is the drupal multi site installation
I am modifying a Bartik theme

drush dl themes and modules  works well
but drush en modulename  and drush cc produces error below;
What needs to be done to fix this please? google is not much help here.
Thanks
Roger

Command cache-clear needs a higher bootstrap level to run - you will [error]
need invoke drush from a more functional Drupal environment to run
this command.
The drush command 'cc' could not be executed.                        [error]
Drush was not able to start (bootstrap) the Drupal database.         [error]
Hint: This error often occurs when Drush is trying to bootstrap a
site that has not been installed or does not have a configured
database.

Drush was attempting to connect to :
   Drupal version    : 7.8
   Site URI          : http://default
   Default theme     : garland
   Administration theme: garland
   PHP configuration : /etc/php.ini
   Drush version     : 4.5
   Drush configuration:
   Drush alias files :
   Drupal root       : /var/www/html/directory
   Site path         : sites/default
   Modules path      : sites/all/modules
   Themes path       : sites/all/themes
   File directory path: sites/default/files
   %paths            : Array

You can select another site with a working database setup by
specifying the URI to use with the --uri parameter on the command
line or $options['uri'] in your drushrc.php file.