Quoting "Roberto C. Sanchez" <roberto@familiasanchez.net>:
Did you remove or purge? Did you also have to drop the database tables? -Roberto
I did remove the packages, not purge. And I did no changes to the database. At first I downgraded horde3 and im4 to the versions in stable. With my current settings that worked already fine. After that I have upgraded again to the latest versions in testing. I think the downgrade was not needed after all.
Butch