I can't read some of my old mail?

There is a chunk of mail, both inbox and sent, over a period of about 2 weeks that I am unable to read. The mail is listed with both title and recipicent/sender but when you go to read it it is then titled [No Subject] and the to as "undisclosed". If I am to list these emails within a search the Title and Recipient are shown together with an extract of the body of the message. This shows the message is still there but I can not retrieve it from the search list either. Sadly, the emails that I am unable to access are important to me! Any ideas?