Apple has withdrawn the server version of its latest Security Update.
MacFixIT is suggesting that the reason for the withdrawal is "severe issues affecting IMAP and APOP e-mail service (caused by a modification to the Cyrus mail service component of OS X server)".
One MacFixIt reader found that following installing the update his server stopped delivering mail. Other readers experienced site compatibility problems in Safari and printer sharing difficulties.
MacFixIt recommends that if the update has been applied it should be removed, and it offers advice on how to do so.