Someone

       CREATE TABLE mos_core_acl_aro (
    ->              aro_id int(11) NOT NULL auto_increment,
    ->              section_value varchar(240) NOT NULL default '0',
    ->              value varchar(240) NOT NULL default '',
    ->              order_value int(11) NOT NULL default '0',
    ->              name varchar(255) NOT NULL default '',
    ->              hidden int(11) NOT NULL default '0',
    ->              PRIMARY KEY  (aro_id),
    ->              UNIQUE KEY section_value_value_aro (section_value(240),value(240)),
    ->              KEY hidden_aro (hidden)
    ->            ) TYPE=MyISAM; 
ERROR 1071 (42000): Specified key was too long; max key length is 1000 bytes