ResolutionThere is a problem with some Mysql packages . They utilize 'mysqladmin ping' to check the MySQL server status but this utility has a bug - it returns wrong status in case of 'Access denied' response (additional information can be found at http://bugs.mysql.com/bug.php?id=3120). Plesk secures MySQL root access with a password, this is why MySQL displays wrong 'failed' status after Plesk is installed.
To fix this, you can do the following:
In the /etc/init.d/mysql file replace the line
MYADMIN="/usr/bin/mysqladmin -uadmin -p'cat /etc/psa/.psa.shadow'"
It will allow the 'mysqladmin ping' command to use the correct Plesk admin login information to connect to MySQL server.