Replies to Outlook message are missing the text
 

I have a few users who are having an issue. When they compose a message in HTML format and send it, some replies they get don't contain any text. When the Message notification pops up, you can see some of the reply text. Also, if you turn on Auto Preview you can see some of the text. But once you actually open the message or view it in the preview pane, you can't see the text. I have tried saving the message as a text document and that didn't work. I tried viewing the source of the reply message and there is nothing in that either.

Outlook is 2003
OS is XP sp2
I haven't been able to determine yet if ISP of the sender.