the logfile ~/.WorkBench/WorkBench.log contains:

2012-10-27 22:42:57,377 INFO Work Bench starting
2012-10-27 22:42:57,393 INFO initLocale ----------------------------------------
2012-10-27 22:42:57,393 INFO LC_ALL is not set
2012-10-27 22:42:57,393 INFO Env DBUS_SESSION_BUS_ADDRESS=unix:abstract=/tmp/dbus-fkDRBlSA2j,guid=fc68a8b01de750552830496a508bf58c
2012-10-27 22:42:57,393 INFO Env DEFAULTS_PATH=/usr/share/gconf/gnome.default.path
2012-10-27 22:42:57,393 INFO Env DESKTOP_SESSION=gnome
2012-10-27 22:42:57,393 INFO Env DISPLAY=:0.0
2012-10-27 22:42:57,393 INFO Env GDMSESSION=gnome
2012-10-27 22:42:57,394 INFO Env GDM_LANG=de_DE
2012-10-27 22:42:57,394 INFO Env GIO_LAUNCHED_DESKTOP_FILE=/usr/share/applications/svn-workbench.desktop
2012-10-27 22:42:57,394 INFO Env GIO_LAUNCHED_DESKTOP_FILE_PID=8519
2012-10-27 22:42:57,394 INFO Env GNOME_DESKTOP_SESSION_ID=this-is-deprecated
2012-10-27 22:42:57,394 INFO Env GNOME_KEYRING_CONTROL=/run/user/sebo/keyring-CWrGix
2012-10-27 22:42:57,394 INFO Env GNOME_KEYRING_PID=1582
2012-10-27 22:42:57,394 INFO Env GPG_AGENT_INFO=/run/user/sebo/keyring-CWrGix/gpg:0:1
2012-10-27 22:42:57,394 INFO Env GTK_MODULES=overlay-scrollbar
2012-10-27 22:42:57,394 INFO Env HOME=/home/sebo
2012-10-27 22:42:57,394 INFO Env LANG=de_DE.UTF-8
2012-10-27 22:42:57,394 INFO Env LANGUAGE=de_DE:en
2012-10-27 22:42:57,394 INFO Env LC_ADDRESS=de_DE.UTF-8
2012-10-27 22:42:57,394 INFO Env LC_IDENTIFICATION=de_DE.UTF-8
2012-10-27 22:42:57,395 INFO Env LC_MEASUREMENT=de_DE.UTF-8
2012-10-27 22:42:57,395 INFO Env LC_MONETARY=de_DE.UTF-8
2012-10-27 22:42:57,395 INFO Env LC_NAME=de_DE.UTF-8
2012-10-27 22:42:57,395 INFO Env LC_NUMERIC=de_DE.UTF-8
2012-10-27 22:42:57,395 INFO Env LC_PAPER=de_DE.UTF-8
2012-10-27 22:42:57,395 INFO Env LC_TELEPHONE=de_DE.UTF-8
2012-10-27 22:42:57,395 INFO Env LC_TIME=de_DE.UTF-8
2012-10-27 22:42:57,395 INFO Env LOGNAME=sebo
2012-10-27 22:42:57,395 INFO Env MANDATORY_PATH=/usr/share/gconf/gnome.mandatory.path
2012-10-27 22:42:57,395 INFO Env PATH=/home/sebo/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games
2012-10-27 22:42:57,395 INFO Env PWD=/home/sebo
2012-10-27 22:42:57,395 INFO Env SESSION_MANAGER=local/sebo-laptop:@/tmp/.ICE-unix/1601,unix/sebo-laptop:/tmp/.ICE-unix/1601
2012-10-27 22:42:57,395 INFO Env SHELL=/bin/bash
2012-10-27 22:42:57,395 INFO Env SSH_AGENT_PID=1651
2012-10-27 22:42:57,395 INFO Env SSH_AUTH_SOCK=/run/user/sebo/keyring-CWrGix/ssh
2012-10-27 22:42:57,395 INFO Env UBUNTU_MENUPROXY=libappmenu.so
2012-10-27 22:42:57,395 INFO Env USER=sebo
2012-10-27 22:42:57,395 INFO Env USERNAME=sebo
2012-10-27 22:42:57,396 INFO Env WINDOWPATH=7
2012-10-27 22:42:57,396 INFO Env XAUTHORITY=/run/gdm/auth-for-sebo-BNJDQP/database
2012-10-27 22:42:57,396 INFO Env XDG_CONFIG_DIRS=/etc/xdg/xdg-gnome:/etc/xdg
2012-10-27 22:42:57,396 INFO Env XDG_CURRENT_DESKTOP=GNOME
2012-10-27 22:42:57,396 INFO Env XDG_DATA_DIRS=/usr/share/gnome:/usr/local/share/:/usr/share/
2012-10-27 22:42:57,396 INFO Env XDG_RUNTIME_DIR=/run/user/sebo
2012-10-27 22:42:57,396 INFO Env XDG_SESSION_COOKIE=35b52b298d98db015aab537150808402-1351349644.312998-355210837
2012-10-27 22:42:57,396 INFO getdefaultlocale -> de_DE, UTF-8
2012-10-27 22:42:57,396 INFO setlocale language_code, encoding -> de_DE, UTF-8
2012-10-27 22:42:57,396 INFO app_name wb_main.py
2012-10-27 22:42:57,396 INFO app_dir /usr/share/svn-workbench
2012-10-27 22:42:57,396 INFO locale set to ('de_DE', 'UTF-8')
2012-10-27 22:42:57,396 INFO locale_path /usr/share/svn-workbench/locale
2012-10-27 22:42:57,397 INFO languages ['de_DE']
2012-10-27 22:42:57,397 INFO find []
2012-10-27 22:42:57,397 INFO info {}
2012-10-27 22:42:57,397 INFO PySVN WorkBench
2012-10-27 22:42:57,397 INFO Reading preferences from /home/sebo/.WorkBench/WorkBench.xml
2012-10-27 22:42:57,749 ERROR EventScheduling<wb_frame.OnUpdateUiSpUpgrade>
Traceback (most recent call last):
  File "/usr/share/svn-workbench/wb_app.py", line 554, in __call__
    result = self.function( *args, **kwds )
  File "/usr/share/svn-workbench/wb_frame.py", line 1074, in OnUpdateUiSpUpgrade
    event.Enable( self.list_panel.list_handler.project_info.need_upgrade )
AttributeError: 'NoneType' object has no attribute 'project_info'
2012-10-27 22:44:06,228 INFO Wrote preferences to /home/sebo/.WorkBench/WorkBench.xml