We had a similar situation about a month or so ago. The user's emails arrived with seemingly no text in the body --or if it was forwarded, blank at the top where her text would have been. Only when someone on the send-to list replied to her email could you see her text. This problem arose corresponding with people in Bali (which we do all the time and so far, only she has ever encountered this issue).
She forwarded me one of the questionable emails, and sure enough I could not see her text.
I gave her a blanket instruction to change her mail format from HTML to Plain Text. This solved the problem--- though I'm not sure what exactly was causing the corruption. She had all of the following (which changing the mail format alleviated)
1. Word as her email editor (compose as HTML)
2. Stationary (yes, she was one of those
3. A cursive signature from hell.