dovecot - Feb 2010 - Folders within folders ...

Our mail setup is as follows:

    ~/mail/ - This contains single mailboxes (Drafts, Trash, and others)
    ~/mail-Archives/ - This contains a hierarchy of folders containing 
mailboxes

    For example, a tree of ~/mail/ would look like this:
       ~/mail/
       ~/mail/Trash
       ~/mail/Drafts
       ~/mail/sent-mail
       ~/mail/My Stuff
       ~/mail/Important
       ~/mail/test/SomeFolder  <-- this would never happen, but I have to
                                   account for it during our transition

    A tree of ~/mail-Archives/ would look like this:
       ~mail-Archives/2009/MyStuff/MyStuff-Dec09
       ~mail-Archives/2009/MyStuff/MyStuff-Nov09
       ~mail-Archives/2009/MyStuff/MyStuff-Oct09
       ~mail-Archives/2010/MyStuff/MyStuff-Jan10
       ~mail-Archives/2010/Important/Important-Jan10

    All of that works, I can open up Thunderbird and browser/read/delete 
messages no problem.  However, when I try to move that 'test' folder 
from ~/mail/ into ~/mail-Archives I get an error message:

       'Can't rename mailbox to another storage type.'

    The same thing happens if I try to move any of the mailboxes in 
~/mail/ to ~/mail-Archives/ .  Is there a way to fix that?  Our 
namespaces look like this:


namespace private {
    separator = /
    prefix = "mail/"
    location = mbox:~/mail:INBOX=/var/mail/%u
    inbox = yes
    hidden = no
    list = yes   # for v1.1+
}

namespace private {
    separator = /
    prefix = "mail-Archives/"
    location = mbox:~/mail-Archives
    inbox = no
    hidden = no
    list = yes
    subscriptions = yes
}