Going to addressbook in Roundcube results in blank page, error 500 reported in developer console and log record in errors log:
PHP Fatal error: Call to a member function get_hierarchy_delimiter() on a non-object in /usr/share/roundcubemail/plugins/libkolab/lib/kolab_storage.php on line 966
That is on Debian Wheeze:

dpkg -l | grep roundcube

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