I tracked this down to the fact that dovecot has apparently changed the default subscriptions file for the maildir backend from .subscriptions to subscriptions. I can't find _any_ documentation of this change, never mind the BIG FLASHING WARNING stuff I would expect. Given that it's too late to revert this change, I think we need to either have dovecot automigrate old '.subscriptions' files or look at both (though then you get into fun issues of which is canonical).
** Changed in: dovecot (Ubuntu) Status: Needs Info => Confirmed -- sub-folders disappear on upgrade from breezy to dapper https://launchpad.net/bugs/51038 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs