installation failing on hostmaster

When attempting an aegir install (automated or manual) in Ubuntu 11.10, I repeatedly run into the following error when hostmaster is being configured; despite entering the appropriate database information when prompted:

!type database type is unsupported. [34.53 sec, 11.56 MB] [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 : 6.22 Site URI : Database driver : Database hostname : Database username : Database name : ://:@: Default theme : garland Administration theme: garland PHP configuration : /etc/php5/cli/php.ini Drush version : 4.4 Drush configuration: /var/aegir/hostmaster-6.x-1.6/drushrc.php Drush alias files : /var/aegir/.drush/hostmaster.alias.drushrc.php /var/aegir/.drush/server_localhost.alias.drushrc.php /var/aegir/.drush/server_master.alias.drushrc.php /var/aegir/.drush/platform_hostmaster.alias.drushrc.php Drupal root : /var/aegir/hostmaster-6.x-1.6 Site path : sites/ Modules path : sites/all/modules Themes path : sites/all/themes %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. [34.53 sec, 11.57 MB] Command dispatch complete [34.53 sec, 11.57 MB] [notice] Peak memory usage was 11.63 MB [34.53 sec, 11.57 MB] [memory] Command dispatch complete [34.53 sec, 10.59 MB] [notice] Peak memory usage was 11.61 MB [34.53 sec, 10.59 MB]