Half my KMail mailboxes are (or were) maildir and half mbox. I was trying
to convert them all to mbox with a view to changing to Evolution. As a
precaution I backed them all up. When I went to restore them, all the sub-
directories were empty. This is the second time this has happened. I am
now using mbox exclusively.

Does anyone know why this is happening?

"It is all right letting yourself go as long as you can let yourself back."
- Mick Jagger.