I have update my Plesk 8.3.0 to 8.4.0 via Plesk Updater: now all my sites show default pagaes of Plesk and my emails doesn't work. My VPS [Rhel3] doesn't run properly "Service is not available now, probably your Plesk is misconfigured. Contact Your provider for details. Internal Plesk error occurred: Components::componentUpdate() failed: Unable to exec utility packagemng: packagemng: Unable to connect to Plesk Database: Client does not support authentication protocol requested by server; consider upgrading MySQL client packagemng: Unable to connect to the mysql database" I have tryed to set OLD_PASSWORD in /etc/my.cnf and mysql> UPDATE mysql.user SET Password=OLD_PASSWORD('*******') -> WHERE Host ='localhost' AND User ='root' ; but nothing changed, except the error message when i TRY to use my Plesk Control Panel "Service is not available now, probably your Plesk is misconfigured. Contact Your provider for details. Internal Plesk error occurred: Unable to connect to database: saved admin password is incorrect." How Can i resolve ? I have mysql4 installed on my VPS: i have to update to mysql5 ? how ? Thank you all!