If you are running horde 3, then you should add this line to your yum.conf main section
exclude=horde imp turba e-smith-horde e-smith-imp e-smith-turba
That way those rpm's will not get installed since for sme 6.x the horde 3 components are installed via a script.
To recover, here is what I would do. Make a backup of your current horde directory, and dump the horde db just in case - mysqldump --opt horde > /root/horde_30.sql. Then in your horde directory, remove the accounts directory. Then run the latest horde 3.0 script. What should happen is the script should see that the accounts directory is not present and proceed to install like it's the first time. You will see some errors as some of the files and RPM's are already installed. After the install, you should be good to go.
Good Luck,
John Bennett