Live Mail – after moving emails to a new folder they all open to the same message

I created a new folder and moved 12 emails into it. When I click on any of the emails they show the same message!

Either that or "A problem occurred while trying to open this message".

So, I copied all the emails in the folder into a new folder, but it has the same problem.

Then I backed up all my Live Mail contacts and messages as a safeguard.

Then I 'repaired' Live Mail, but this made no difference to this folder of email messages.

Any ideas please?

Michael