PDO does not trow Exceptions for queries

$C->DB is my connection, but no exceptions will be thrown for the last
queries - althogh there is an error (whoch the command line would show).
Is there another option to activate throwing of exceptions?

$C->DB->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);

$C->DB->query('DROP TABLE key');

$C->DB->query('CREATE TABLE key ( id SERIAL NOT NULL PRIMARY KEY, k TEXT
NOT NULL UNIQUE )');

$S = $C->DB->prepare('INSERT INTO key (k)
SELECT lower(k) FROM current_node_tags LIMIT 100');

What my phpinfo() says:

PHP Version 5.2.6-1+lenny3

This server is protected with the Suhosin Patch 0.9.6.2

PDO
PDO support enabled
PDO drivers pgsql

pdo_pgsql
PDO Driver for PostgreSQL enabled
PostgreSQL(libpq) Version 8.3.7
Module version 1.0.2
Revision $Id: pdo_pgsql.c,v 1.7.2.11 2006/03/14 10:49:18 edink Exp $

pgsql
PostgreSQL Support enabled
PostgreSQL(libpq) Version 8.3.7
Multibyte character support enabled
SSL support enabled
Active Persistent Links 0
Active Links 0
pgsql.allow_persistent On On
pgsql.auto_reset_persistent Off Off
pgsql.ignore_notice Off Off
pgsql.log_notice Off Off
pgsql.max_links Unlimited Unlimited
pgsql.max_persistent Unlimited Unlimited