To fix this remove the current horde database and recreate a new one. Follow the below steps,
cd /var/lib/mysql
mysqldump horde > horde.sql
mysqladmin drop horde
/scripts/fullhordereset
mysqlcheck -r -o horde
Now logout and login to Horde.
cd /var/lib/mysql
mysqldump horde > horde.sql
mysqladmin drop horde
/scripts/fullhordereset
mysqlcheck -r -o horde
Now logout and login to Horde.