[horde] IMP, Cyrus and IMAP folder sharing

[Stoyan Tzalev]

Hi guys,
I'm trying to use horde's ability to manage IMAP shared folders and (I think) 
I'm almost there -  it displays and successfully changes any previously 
created (via cyradm) ACLs. The thing is I'd like to be able to create new 
entries and delete old ones. I guess this is something that is already 
thought of, as there's a drop-down menu, probably for creating new users. The 
trouble is that it is empty - the element is there, but it doesn't contain 
anything. 
Can someone please point me in the right direction to look? Or should I 
provide more info?

Best regards,
Stoyan

P.S.
Here's some info about my setup - 
the authentication driver is cyrsql, and servers.php contains this:

$servers['cyrus'] = array(
    'name' => 'Cyrus IMAP Server',
    'server' => 'localhost',
    'hordeauth' => 'full',
    'protocol' => 'imap/notls',
    'port' => 143,
    'maildomain' => '',
    'smtphost' => 'localhost',
    'smtpport' => 25,
    'realm' => '',
    'preferred' => '',
    'admin' => array(
        'params' => array(
            'login' => 'cyradmin',
            'password' => 'cyradmin_pass',
            // The 'userhierarchy' parameter defaults to 'user.'
            // If you are using a nonstandard hierarchy for personal
            // mailboxes, you will need to set it here.
            'userhierarchy' => 'user/',
            // Although these defaults are normally all that is required,
            // you can modify the following parameters from their default
            // values.
            'protocol' => 'imap/notls',
            'hostspec' => 'localhost',
            'port' => 143
        )
    ),
    'quota' => array(
        'driver' => 'imap',
        'params' => array('hide_quota_when_unlimited' => true),
    ),
    'acl' => array(
        'driver' => 'rfc4314',
    ),
);