I got hit by the same issue - even tried apr-get remove --purge and reinstall of nagios-plugins.
Same error message with a zero-sized /etc/nagios-plugins/config/imap.cfg did a workaround of echo '# Dummy' >> /etc/nagios-plugins/config/imap.cfg and it seems to work OK -- Andrew Elwell, System Administrator EPCC Tel 0131 445 7833 (ACF Building) Tel 0131 650 5023 (Rm 3309, JCMB) -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of "unsubscribe". Trouble? Contact [EMAIL PROTECTED]