Outlook 2007 problem

I am experiencing a strange issue. When a user sends an email to whomever and they reply the message has no new text other than there original message. The actually reply in the email is missing. There is no pattern as it is affecting multiple users randomly. The email is hosted with an ISP and they are all running Outlook 2007. Well actually some are using the webmail client provided by the ISP. Any thoughts or suggestions would be great.