Did you get any errors during the upgrade? Can you try upgrading to 5.5.3 (released yesterday)?
First reproduce the issue, then look in /var/log/httpd/error_log or /var/log/httpd/ssl_error_log, do you see any errors that may be related?
Are you seeing any crashed tables in /var/log/mysqld.log or in /var/log/mariadb/mariadb.log? If so, please try repairing the DB tables:
https://support.nagios.com/kb/article.php?id=24
We might want to move this into a ticket so we can setup a remote session if you are not seeing anything.
Did you logout, close the browser and reopen it?