Hi,
About bug referenced at http://sourceforge.net/tracker/index.php?func=detail&aid=1334954&gro...
I have debugged the session script: it tries to SELECT 1 if the session_id already exists, then UPDATE it or INSERT it. The problem is that the session id is encrypted with 32 or 40 characters, depending running php version. Then the field session.sess_id must be a VARCHAR(40), not VARCHAR(32) else Roundcubemail will never catch an already created session and will try to insert another one with the same primary key (what MySQL forbidens).
Using today's CVS, latest stable PHP-5, FreeBSD 4.8