Creating subfolders on an IMAP server (bincimapd) using thunderbird

I am running Debian (Lenny/Testing), and the Icedove (unbranded version
of Mozilla Thunderbird).

I have connected to the IMAP mail server, and I have a folder view as
follows:

-+ mark
-- Inbox (120)
-+ Local Folders
-- Unsent
-- Trash

I want to create a subfolder "Processed" as follows:

-+ mark
-- Inbox (120)
-- Processed
-+ Local Folders
-- Unsent
-- Trash

I apply a rightclick mouse event to my username (mark), and then
Menuitem: New Folder, Prompt: Name> Processed, Prompt: Create as a
subfolder of> mark, Button: OK

No "Processed" subfolder appears. How do I create the subfolder?

My IMAP server is bincimap, if that is important.

I look at the error console on icedove, using Mainmenu> Tools, Error
Console, Button: All

There are no errors showing on the icedove error console.

I examine the syslog on the server machine, and all it shows is:

Dec 24 09:38:46 charon bincimap-up[28675]: connection from ?
Dec 24 09:39:06 charon bincimapd[28676]: <mark> authenticated

What is wrong? How do I create the subfolder?

Mark.

--
Mark Hobley
Linux User: #370818 http://markhobley.yi.org/

.