[Dovecot] Upgrading from 1.2.8 to 2.0.6: INBOX not selectable in Thubderbird (greyed and italic)

[Michele Bergonzoni]

I recently upgraded from 1.2.8 to 2.0.6, I am using Maildir, and 
Thunderbird is showing the INBOX grayed out and in italics, and does not 
show new messages in it (it shows messages previously downloaded). This 
occurs when Thunderbird is restarted (if I upgrade dovecot, TB keeps 
working fine until I shut it down, and at next startup it greys out the 
inbox). All the subfolders of INBOX work fine. Accessing with horde+imp 
webmail works fine. I'm using TB 3.1.6

After some traffic capturing, The first difference I see in the IMAP 
exchange is the answer to

6 list "" "INBOX"

Which for 1.2.8 is:
LIST (\HasChildren) "." "INBOX"

and for 2.0.6 is:
LIST (\Noselect \HasChildren) "." "INBOX"

Of course for the same user and same maildir. I enabled 
tb-extra-mailbox-sep in 2.0, but it doesn't appear to differ (I don't 
really think it should).

Any help will be very much appreciated. My 1.2.8 config for the 
namespaces is:

namespace private {
  prefix = INBOX.
  inbox = yes
  location = maildir:~/Maildir
}

namespace public {
  prefix = shared.
  location = maildir:/usr/local/shared
  list = yes
  subscriptions = no
}

And the config for 2.0.6 is the same with new syntax:

namespace {
  type = private
  prefix = INBOX.
  inbox = yes
  location = maildir:~/Maildir
}

namespace {
  type = public
  prefix = shared.
  location = maildir:/usr/local/shared
  list = yes
  subscriptions = no
}

Regards,

                                    Michele Bergonzoni