[Dovecot] cant see public mailbox

[spamvoll at googlemail.com]

hi..

im running dovecot 2.0.1

sharing mailboxes works like a charm, but now im trying to create a
public undetected-SPAM folder.
thunderbird shows the public namespace but no mailboxes.
ive created the public folder and did a mkdir for the folder..
after that doesnt work ive created cur,new,tmp in .undetected-SPAM

/home/MAILBOXES/public# ls -al
drwx------  3 vmail vmail   74  7. Sep 14:23 .
drwxr-xr-x 57 vmail vmail 4096  7. Sep 14:23 ..
-rw-------  1 vmail vmail    0  7. Sep 14:23 dovecot-acl-list
-rwx------  1 vmail vmail    0  7. Sep 13:19 dovecot-shared
drwx------  5 vmail vmail   36  7. Sep 14:17 .undetected-SPAM

doveconf -n
mail_location = maildir:~/mail
namespace {
  inbox = yes
  location =
  prefix =
  separator = /
  type = private
}
namespace {
  list = children
  location = maildir:%%h/mail:INDEX=~/mail/shared/%%u
  prefix = shared/%%u/
  separator = /
  subscriptions = no
  type = shared
}
namespace {
  list = children
  location = maildir:/home/MAILBOXES/public:INDEX=~/mail/public
  prefix = public/
  separator = /
  subscriptions = no
  type = public
}

any ideas ?

Hans