php pdo ¿What am I doing wrong?

I'm learning php pdo; my environment is : NetBeans 6.5.1, XAMPP 1.7.0 and I have this code, which it seems to connect.

• If I change dbname to a non existent one, it raises exception "db not exists"
• If I change user, it raises "login incorrect")

but when I call $cn->query, it raises:

An unhandled Win32 exception occurred in apache.exe

What am I doing wrong?

$hostname = 'localhost';
$username = 'crb';
$password = 'letmein';
try {
    $cn = new PDO("mysql:host=$hostname;dbname=bitacora", $username, $password);
    echo 'Connected to database<br />';
    $sql = "SELECT * FROM usuario WHERE login = '".$login."' AND clave = '".$clave."'";
    // Error here
    foreach ($cn->query($sql) as $row) {
        print $row['login'] .' - '. $row['clave'] . '<br />';
    }
} catch (PDOException $e) {
    echo $e->getMessage();
} catch (Exception $e) {
    echo $e->getMessage();
}

From stackoverflow

• Is $cn valid? Check the return value. What you've described so far doesn't convince me that you're connected.

  Jhonny D. Cano -Leftware- : in NetBeans debug watch says it is object, what else should I check?

  John at CashCommons : Do you handle exceptions? catch(PDOException $e) {echo $e->getMessage();}

  Jhonny D. Cano -Leftware- : Yes, it doesn't raise exception, nor creating connection, neither doing cn->query it raises apache error

• This is a bug in XAMPP 1.7.0. Upgrade to 1.7.1 or follow these instructions to fix your 1.7.0 installation.

• If you haven't already, I'd make sure your environment was working right.

  1. Check to make sure the user works with MySQL itself (using something like mysqlquery).
  2. Check to make sure php can connect to MySQL. I install phpmyadmin on all new setups (even if I don't leave it in place) to make sure I have a good working connection.
  3. Have PDO through exceptions on errors (see http://us2.php.net/manual/en/pdo.error-handling.php) to see where the errors are occurring right away.

  My guess is that you are not ever connecting to MySQL, which would explain the inability to change the database.