[Dovecot] read() failed with subscription file

Hello Dovecot folks, I have Dovecot running reasonably well against my Postfix SMPTd. All mail is stored in Maildir format only. In my Thunderbird client I can see the Inbox, Trash and Sent folders in the Thunderbird pane but no other directories. I have very many Maildir format directories under my Inbox directory but I cannot see them in the Thunderbird client. I have the Dovecot info and debug log runnning with the solitary error message being displayed in the log when ever I access the Thunderbird client folders pane as stated below. Particulars follow and please advise, David.

OS: CentOS 5.2 Postfix: 2.3.3 Dovecot: 1.2

Dovecot log: dovecot: IMAP(user): read() failed with subscription file /home/user/Maildir/subscriptions: Is a directory