The changelog's top comment is stamped 2007-01-05, 18:48 if that helps nail down the version (I'm using a Debian/Ubuntu package).
dovecot --version will tell you the exact version. Why guess?
Both non-SSL and SSL logins have the problem.
The version you are using is very old with respect to dovecots current state. Iirc, there were *many* changes to do with ldap, ssl and login issues that are fixed in current releases.
Please find a current release (rc29 is the current one), and see if that fixes your problems.
-- Best regards, Charles
