undefined function pg_connect()

Hello,

I wonder if someone could help me resolve this problem.

Today, after upgrading from PHP 5.2.3. to 5.2.6, this little program:

<?php
        $db = pg_connect('host=localhost dbname=xxxx user=chubb
password=yyyyyy')
            or die('Could not connect: ' . pg_last_error());
?>

is now getting this error:

*Fatal error*: Call to undefined function pg_connect() in *
C:\Inetpub\cu\code_tests\db_connect.php* on line *2

*
According to phpinfo() ...

Server API: ISAPI
Loaded Configuration File: C:\Program Files\PHP\php.ini
PHP Extension: 20060613
Path environment variable: C:\Program
Files\PHP\;C:\WINDOWS\system32;C:\WINDOWS;C:\WINDOWS\System32\Wbem;C:\Program
Files\QuickTime\QTSystem\

In the php.ini file, I do have:
extension=php_pgsql.dll

And on my system, I do have:
C:\Program Files\PHP\ext\php_pgsql.dll   (98,368   2008-05-02 18:07)

I am running Windows/XP and IIS 5.1.

What is causing this problem?

Many thanks
jfc