PDO drivers not loading in PHP 5.4.0

Hi all,

I downloaded the latest windows build from http://windows.php.net/downloads/releases/php-5.4.0-Win32-VC9-x86.zip
but I can't make the PDO drivers to load. I have uncommented the appropriate lines in php.ini (extension=php_pdo_mysql.dll)
but no luck. When running phpinfo(), under section PDO I get:

PDO drivers no value

I'm using apache 2.2.22 that I downloaded from http://www.apachelounge.com/download/win32/bins/httpd-2.2.22-win32.zip
PHP version 5.3.8 works fine with the same apache install.
OS is Windows 7.

Thanks,
Pavle.