Header.txt text missing in repeatable case

Can you help me troubleshoot this SmartList problem? I searched the smartlist archives but couldn't find reference to this... Problem: Text in the header.txt file is -not- included in an email if a file is attached to the email. Additional information: * The problem does not happen if the email does not include any attachments. * The proper SmartList files are set up (header.txt, rc.custom and rc.local.s20) correctly because the header text does display in emails without attachments. I don't know where to start troubleshooting this. I just started using the basic features of SmartList for 'announcement-only' emails to a mailing list. Can you point me to where the cause might be? Thanks in advance. Abbo