Title says it all - same applies to the menu. I've checked settings in "configure kmail" but nothing jumped out at me. I also tried removing ~/.kde4/share/apps/kmail/kmail_part.rc but no joy.

If anybody has any pointers I'd be very grateful!

Thanks in advance.

Is this across all folders or just the Sent mail folder?
There was a fix in KDE 4.3 for not being able to reply to messages in a Sent mail folder.

You could also try manually enabling it by making the appropriate "enable" call to the reply action over D-Bus.
Also try removing any State= from the configuration file.

The greyed out "reply" is only in the inbox. I can reply from other folders.

Your other suggestions are a little above me, I am afraid. But thanks very much for the hint re KDE4.3 - I reckon I will just have to bite the bullet and wait.