This error is when you install slapd -> remove slapd -> reinstall slapd.
You can around the problem installing manually
1) dpkg --install libldap-2.4-2_2.4.23-0ubuntu3_amd64.deb
2) dpkg --install slapd_2.4.23-0ubuntu3_amd64.deb
3) apt-get dist-upgrade
This error is when you install slapd -> remove slapd -> reinstall slapd. 2.4-2_2. 4.23-0ubuntu3_ amd64.deb 4.23-0ubuntu3_ amd64.deb
You can around the problem installing manually
1) dpkg --install libldap-
2) dpkg --install slapd_2.
3) apt-get dist-upgrade
I confirm this problem on ubuntu 10.10 amd 64