Version:           1.7.1 (using KDE 3.3.1,  (3.1))
Compiler:          gcc version 3.3.5 (Debian 1:3.3.5-3)
OS:                Linux (i686) release 2.6.9-1-686

When I click a message header in the mail list pane, the message does not always display in the mail pane.

I think this is an IMAP problem. It only seems to happen when I select a new message in an IMAP folder. When I say "new," I mean that it's not a message I have read before. The actual read/unread state makes no difference.

Selecting another message, then selecting the first one again allows me to see it. Once I have viewed the message, everything works normally.

Keyboard shortcuts act the same way. If I select a new message in a thread, read it, then press 'n' (or the spacebar at the bottom of the message), the next mail is highlighted, but not displayed.

This is on a Courier IMAP server. It wasn't a problem with earlier versions of KMail, but I'm not positive at what version things broke. I think it surfaced in 3.3.0.