1. Start KMail
2. Hit new e-mail
3. Try to enter a recipient
The entry field was shortly there but then dissapeared. When moving the flap back in the composer textentry field was also gone.
This is not always reproducable but it happens from time to time.
Assuming that the main text entry field disappeared, this is a duplicate.
(But even if the entry fields of the recipients dissappeared, this is likely the same issue.)
*** This bug has been marked as a duplicate of bug 260882 ***