[binc] "Lost" folders with Thunderbird

Hi,
I've got a server with bincimap and qmail.
On the client side i use Thunderbird.

I've made some subfolders at the Inbox and puted all my mails into this
folders. After restarting Thunderbird i can't see these folders.
On the console i can see the folders
~/.maildir$ ls -a
.bincimap-subscribed
.subfolder1
.subfolder2
bincimap-cache
bincimap-uidvalidity
cur
new
tmp

As depot i use Maildir++ but i've tryed IMAPdir with the same result.
I've also added "INBOX/" to the "IMAP server directory" in thunderbird,
also with the same result.

Has anyone an idea how to get the subfolders "back"?

Regards,
Raphael