Roundcube - kolab_files plugin

Hi,

I found repeated erros in
/var/log/roundcubemail/errors.log file.

The errors are from kolab_files roundcube plugin.
The errors are shown repeatedly when entering individual folders in any 
user mailbox.

PHP Error: Authenticate error (Status: 500) in 
/usr/share/roundcubemail/plugins/kolab_files/lib/kolab_files_engine.php 
on line 1017
PHP Error: Failed to get capabilities. Status: 500 in 
/usr/share/roundcubemail/plugins/kolab_files/lib/kolab_files_engine.php 
on line 1050

Sometimes there are two other errors:
PHP Error: LDAP: ldap_search failed for dn=ou=People,dc=. No such object
LDAP Error: DN not found using LDAP search.

I'm using 3 domains in my kolab installation.
I followed multidomain setup docs.

Despite the errors, it looks like evrything working.
But I would like to have no errors, it would be better :).

Has someone any idea?
Thanks.

Thomas