have you tried to run the mysql_upgrade
script after upgrading ?
sudo mysql_upgrade --password=root-password-here
if doesn't let you run the script , start mysql server with --skip-grant-tables
sudo /usr/sbin/mysqld --skip-grant-tables &
and after that
sudo mysql_upgrade --force
i think your problem is a bug discussed here http://bugs.mysql.com/bug.php?id=60432