[Users] Enter key required before full message appears

[Cliff Laine]

Would anyone know why I have to press the enter key before message
bodies appear? 

The behaviour is: open CM (which automatically opens my main
account's inbox), and the first message in the list of messages is
highlighted, but the message pane remains blank until I press the Enter
key.

Cliff

CM 3.8.0 (GTK+ 2.18.3; i486-pc-linux-gnu) 
Linux Mint 14 
KDE 4.9.4