See how Jan-July and Aug-Dec are still directories underneath the Maildir
directory even though in the IMAP structure they are underneath 2005?
Gotcha, but they're not showing up there either!
Anyways, I think you borked something with your copying over... What
command did you use? Your subfolders of "Mailing Lists" should appear
when you do a ls -al in Maildir if they got copied over at all. If they
didn't get copied but still were listed in courierimapsubscribed then
you'd get an error similar to what you're reporting...
I just used a simple cp -r from the old location to the new. That
should have done the trick, no?
I'm tempted to give it another shot, but is there any way to hold onto
the messages that have come in since this new installation started
working? (It's not critical, but it would be nice.)