[Dovecot] target doesn't allow inferior mailboxes

[Adam Williams]

Using Seamonkey as my email client, and IMAP to check mail.  If I create 
a new IMAP folder, and then delete it, I get the error:

The current command did not succeed. The mail server responded: Target 
mailbox doesn't allow inferior mailboxes.

Tried a google search, didn't really come up with anything.  I have rw 
permissions on /home/awilliam/Mail/* and delete the files fine using rm 
-rf /home/awilliam/Mail/whatever and editing the folder out of 
.subscriptions.  Any ideas?

[root at roark ~]# dovecot --version
1.0.1
[root at roark ~]# dovecot -n
# 1.0.1: /etc/dovecot.conf
login_dir: /var/run/dovecot/login
login_executable(default): /usr/libexec/dovecot/imap-login
login_executable(imap): /usr/libexec/dovecot/imap-login
login_executable(pop3): /usr/libexec/dovecot/pop3-login
mail_location: mbox:~/Mail/:INBOX=/var/spool/mail/%u
mail_executable(default): /usr/libexec/dovecot/imap
mail_executable(imap): /usr/libexec/dovecot/imap
mail_executable(pop3): /usr/libexec/dovecot/pop3
mail_plugin_dir(default): /usr/lib/dovecot/imap
mail_plugin_dir(imap): /usr/lib/dovecot/imap
mail_plugin_dir(pop3): /usr/lib/dovecot/pop3
auth default:
  passdb:
    driver: pam
  userdb:
    driver: passwd