Some Message bodies not displayed in Inbox folder list.

Previously, my view of the Inbox folder displayed all messages, with the message header plus the message body contents. Now, some (but not all) messages display just the header but not the message body, and when I select the messages, the focus indicates that TB is viewing a different (usually the immediately-preceding) message, and NO contents/body are visible. I have tried to find out what is in the non-displayed message, and to force TB to focus on the offending message, but have had no success. From the message subject and header, some of these messages are important to me. How can I force TB to display them like it does the other messages. NOTE: Nothing in the message header indicates the messages with this problem are any different from the messages that are properly displayed.