Drupal6 installs, but can't connect with database

Binary package hint: drupal6

I installed the packages drupal6 (6.16-1) and dh-make-drupal (0.5-1) in my Lucid and the install process run without errors:
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Selecionando pacote previamente não selecionado dh-make-drupal.
(Lendo banco de dados ... 295416 arquivos e diretórios atualmente instalados).
Desempacotando dh-make-drupal (de .../dh-make-drupal_0.5-1_all.deb) ...
Selecionando pacote previamente não selecionado drupal6.
Desempacotando drupal6 (de .../drupal6_6.16-1_all.deb) ...
Processando gatilhos para man-db ...
Configurando dh-make-drupal (0.5-1) ...
Configurando drupal6 (6.16-1) ...
dbconfig-common: writing config to /etc/dbconfig-common/drupal6.conf

Creating config file /etc/dbconfig-common/drupal6.conf with new version

Creating config file /etc/drupal/6/sites/default/dbconfig.php with new version
creating postgres user drupal6: success.
verifying creation of user: success.
creating database drupal6: success.
verifying database drupal6 exists: success.
dbconfig-common: flushing administrative password
www-data www-data 750 /var/lib/drupal6/files

Pressione Enter para continuar.
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After that I needed to change /etc/apache2/sites-available/default to include the drupal alias and directory (this shouldn't be done by the install process?):
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    Alias /drupal/ "/usr/share/drupal6/"
    <Directory "/usr/share/drupal6/">
        Options Indexes MultiViews FollowSymLinks
        AllowOverride None
        Order deny,allow
        Deny from all
        Allow from 127.0.0.0/255.0.0.0 ::1/128
    </Directory>
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Then I tried to run the install.php script, but I receive this error:
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The following error must be resolved before you can continue the installation process:
Failed to connect to your PostgreSQL database server. PostgreSQL reports the following message: Connection failed. See log file for failure reason.

    * Are you sure you have the correct username and password?
    * Are you sure that you have typed the correct database hostname?
    * Are you sure that the database server is running?
    * Are you sure you typed the correct database name?

For more help, see the Installation and upgrading handbook. If you are unsure what these terms mean you should probably contact your hosting provider.
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I checked the dbconfig.php file but it looks correct (the user name and password are only for test purposes):

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# cat /usr/share/drupal6/sites/default/dbconfig.php
<?php
##
## database access settings in php format
## automatically generated from /etc/dbconfig-common/drupal6.conf
## by /usr/sbin/dbconfig-generate-include
## Thu, 21 Oct 2010 11:29:09 -0200
##
## by default this file is managed via ucf, so you shouldn't have to
## worry about manual changes being silently discarded. *however*,
## you'll probably also want to edit the configuration file mentioned
## above too.
##
$dbuser='drupal6';
$dbpass='passwordrupal6';
$basepath='';
$dbname='drupal6';
$dbserver='';
$dbport='';
$dbtype='pgsql';
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(filling dbserver and dbport values does not solve the problem)

Both my Apache and Postgres installations are default. I've installed a PHP software called LimeSurvey (manually, it does not have a package) and it worked perfectly with Postgres.

There is no significant error message both in Apache's error.log and Postgres postgresql-8.4-main.log.

I think there is something wrong with Drupal package, it should work right out of the box.

I purged the packages, removed the database and the user and tried again with the same result.