When you choose the mcrypt library to be added to the apache/php install from within cpanel/whm it will actually install them in another path and not update the php.ini file.
This means that the CBC.php file will never be found unless:

1. cpanel changes the way mcrypt is intalled
or
2. you add the following line to the path variable in php.ini
:/usr/local/cpanel/3rdparty/lib/php

Any comments from the cpanel team?

cPanel.net Support Ticket Number: