Finally! I got my Linux box with my mail server back up and running. It seems the version of the Berkeley Database (BDB) that was installed in the update caused the LDAP and IMAP applications fits.

The fix for the IMAP server was easy: run the db42_recover command and zap the log file.

Unfortunately, I had to delete the LDAP server database and re-enter the entries by hand. Ouch! Lesson learned: periodically use slapcat to create a backup copy of the LDAP data.