PDO_MYSQL connect fallback from localhost do /tmp/mysql.sock

Hi! I have a strange problem when connecting to a MySQL 4.0.24 server using PDO_MYSQL (from PHP 5.1.6). I tried the following code: <?php new PDO('mysql:host=localhost;dbname=test'); ?> And the error is: SQLSTATE[HY000] [2002] Can't connect to local MySQL server through socket '/tmp/mysql.sock' (2)' If I change the hostname to the external name: <?php new PDO('mysql:host=example.com;dbname=test'); ?> it works. In my.cnf "socket" is set to /var/run/mysqld/mysqld.sock, not /tmp/mysql.sock. There is no php.ini loaded, the precompiled mysql library from MySQL AB has been used. In phpinfo() the setting "MYSQL_SOCKET" from the old mysql extension says /tmp/mysql.sock! Do you have any idea what is going wrong here? Should I file a bug report? best regards Andreas