Microsoft Outlook 2003 Error 0x8004DF0B has been plagueing me for a long time.  I have a couple of clients using Outlook in a bunch of different offices, and connecting into more-or-less out-of-the-box Courier IMAP setups on FreeBSD, with client SSL enabled for both inbound (imaps) and outbound email (both smtp with starttls and Outlook's poxy smtps/465).

The problems started when I installed NOD32 Antivirus. On a fairly regular basis, the Outlook installation would start reporting the following error: