Ré-Installation Joomla

Bonjour,
Suite à la reinstallation de joomla sur un nouvel hébergement, j'obtiens ceci :

Warning: session_start() [function.session-start]: Cannot send session cookie - headers already sent by (output started at /homez.85/openmult/castel-info/configuration.php:1) in /homez.85/openmult/castel-info/libraries/joomla/session/session.php on line 412

Warning: session_start() [function.session-start]: Cannot send session cache limiter - headers already sent (output started at /homez.85/openmult/castel-info/configuration.php:1) in /homez.85/openmult/castel-info/libraries/joomla/session/session.php on line 412

Warning: Cannot modify header information - headers already sent by (output started at /homez.85/openmult/castel-info/configuration.php:1) in /homez.85/openmult/castel-info/libraries/joomla/session/session.php on line 415

Warning: Cannot modify header information - headers already sent by (output started at /homez.85/openmult/castel-info/configuration.php:1) in /homez.85/openmult/castel-info/plugins/system/jfrouter.php on line 333

Warning: Cannot modify header information - headers already sent by (output started at /homez.85/openmult/castel-info/configuration.php:1) in /homez.85/openmult/castel-info/plugins/system/jfrouter.php on line 334

Warning: Cannot modify header information - headers already sent by (output started at /homez.85/openmult/castel-info/configuration.php:1) in /homez.85/openmult/castel-info/plugins/system/jfrouter.php on line 335

Avez-vous une idée d'où ça peux venir ?
Merci