Issue after provider changed serveur/db
You need to delete /media/civicrm/civicrm/ConfigAndLog/Config.IDS.ini file. 

This will fix the issue.

This is clearly mentioned in Step 9 in the docs - http://wiki.civicrm.org/confluence/display/CRMDOC/Moving+an+Existing+Installation+to+a+New+Server+or+Location . Make sure you (your provider) follow these instructions when moving CiviCRM to new server/location