I just started seeing this occur today. When I started Thunderbird, my main e-mail has the subject matter, date and time, but doesn't display the message. All my other e-mail identities are unaffected. All e-mails from previous dates are displayed properly. New messages today are displayed correctly. I tried to forward one of the messages to another address, and it came out blank. I tried starting it in Troubleshooting mode, but it made absolutely no difference. How do I view the messages?