Diacritical marks are truncated via Active Record

This must be a charset problem. Have you checked that your database connection is utf8, that your files (controller, views, etc.) are saved as uft8? And in your /application/config/database.php should be also the utf8 :

Code:

    'char_set' => 'utf8',
    'dbcollat' => 'utf8_general_ci',

And your database should have this encoding: utf8_general_ci