Multi-Db installation


I have installed Multi-DB (4096). After triple check (installation, procedure),I have moved blogs. Everything is okay. I have checked PhpAdmin, the blogs are there. Unfortunately when I go to my url, I got this error :

Warning: mysql_get_server_info(): supplied argument is not a valid MySQL-Link resource in /home/mysite/www/wp-content/db.php on line 669

Warning: Cannot modify header information – headers already sent by (output started at /home/mysite/www/wp-content/db.php:669) in /home/mysite/www/wp-includes/functions.php on line 3191

Error establishing a database connection

I have to delete the file db.php, and then my site is visible. I would need your expertise please…