Changes have been made in Git (master):

commit 8f7984f36dd4bfcd5374693003f3773af9782b20
Author: Michael J Rubinsky <mrubinsk@horde.org>
Date:   Sun Sep 29 12:32:04 2013 -0400

     Bug: 12718 Fix sourceselect pref handler.

  whups/config/prefs.php |    3 ++-
  1 files changed, 2 insertions(+), 1 deletions(-)

http://git.horde.org/horde-git/-/commit/8f7984f36dd4bfcd5374693003f3773af9782b20

Horde 5.1.2
Whups Version: 3.0.0RC2: Whups H5 (3.0.0) Release Candidate 2

All is running properly but if the user is going to his settings and 
then to adress book the following will occured:
Ein schwerer Fehler ist aufgetreten:
Missing or invalid type option for the sourceselect preference.

1. Horde_Core_Prefs_Ui->generateUI() /var/www/horde/services/prefs.php:32

Details
Die vollständige Fehlermeldung wurde in Hordes Logdatei geschrieben 
und für Administratoren weiter unten ausgegeben. Benutzer, die keine 
Administratoren sind, bekommen diese Details nicht zu sehen.

Horde_Exception Object
(
     [details] =>
     [logged] => 1
     [_logLevel:protected] => 0
     [message:protected] => Missing or invalid type option for the 
sourceselect preference.
     [string:Exception:private] =>
     [code:protected] => 0
     [file:protected] => /usr/share/php/Horde/Core/Prefs/Ui.php
     [line:protected] => 581
     [trace:Exception:private] => Array
         (
             [0] => Array
                 (
                     [file] => /var/www/horde/services/prefs.php
                     [line] => 32
                     [function] => generateUI
                     [class] => Horde_Core_Prefs_Ui
                     [type] => ->
                     [args] => Array
                         (
                         )

                 )

         )

     [previous:Exception:private] =>
)



And in the logfile i found:

HORDE: [whups] Missing or invalid type option for the sourceselect 
preference. [pid 23248 on line 581 of 
"/usr/share/php/Horde/Core/Prefs/Ui.php"]

This is a complete new installation, no migration.