ldap error while accessing roundcube addressbook. Help for debugging

[Jan Kowalsky]

Hi all,

I'd like to ask people for help while debugging my roundcube installation.

Since any update or change of configuration (I can't remember exactly when it 
appeared first) I get the error:

LDAP Error: Bind  failed for dn=uid=kolab-service,ou=Special 
Users,dc=example,dc=net: Can't contact LDAP server in 
/usr/share/roundcubemail/program/lib/Roundcube/rcube_ldap_generic.php on line 
285 (GET /roundcubemail/?_task=addressbook)

in /var/log/roundcube/errors 

when I try to access the address book in roundcube.

Everything else works. So the connection to ldap-server is working at all.

I took a look in 
/usr/share/roundcubemail/program/lib/Roundcube/rcube_ldap_generic.php
but actually don't understand how to get more infos for debugging, eg. to 
which host it tries actually to connect.

I already set the debug-level in roundcube to 5

(Debian 7.0 with kolab 3.1 and roundcubemail 1:1.0~dev20131125-1~kolab1)

Thanks for any hint.

Best regards
Jan