Version:            (using KDE KDE 3.3.0)
Installed from:    FreeBSD Ports
Compiler:          gcc 2.95.3, unless the FreeBSD port requests something later (which I don't think it does) 
OS:                FreeBSD

Under some circumstances that I don't understand (but rather often),
selecting an unread mail message in my IMAP inbox neither shows it
in the preview pane nor marks it as read. This has happened when
the selection was done
  - by clicking with the mouse;
  - by pressing "n" to move to the next message;
  - by applying a filter that moves the current message into
    a different folder, making a later message current.

Clicking on the message again doesn't make any difference. Selecting
a different message first and then the original one again (either with
the mouse or, e.g., the keys p,n) reliably selects the message
properly -- i.e., previews it and marks it read.

This sounds similar to bug 88511, but seems to differ from it in
at least the following ways:
  - Selecting a different message consistently makes that message
    appear in the preview pane.
  - I have not found it necessary to select a different folder
    to get the messages to appear.

The behaviour is not consistent, in that sometimes selecting a new
message works absolutely fine. However, it seems to be "bursty";
if I have a block of new messages and KMail misbehaves on the first
one, it will generally do so on the second as well. Unfortunately
I haven't yet discerned what it is that breaks this pattern. I *think*
(with very little confidence) that the failure commonly begins when I
filter away some messages.

I do not think this has ever happened with an already-read message.

I have only observed this in my inbox (which, as I say, is an IMAP one,
talking to a MS Exchange 5 server) and not in any other folder. I spend
much longer in my inbox than elsewhere, though, so this is not strong
evidence that it can't happen elsewhere.

This has happened to me ever since installing KDE 3.3 (built from
the FreeBSD ports collection without specifying any special flags,
environment variables, etc.). I don't recall it ever happening in
earlier versions of KMail.

I'd love to give a repro recipe, but I don't have one. :-)

I'm running KMail in pretty much its default setup. No plugins.
I'm *not* running it in a full KDE environment; I'm using the Ion
window manager.

There's nothing obviously relevant in such debugging output as I
have, although I often get the following line
    kmail: WARNING: KMMessagePart::bodyDecoded(): body is binary but used as text!
output to whatever-I-ran-kmail-from when I select a new message.
(I haven't looked for any correlation between this and the bad
behaviour mentioned above, but it certainly sometimes happens when
that bad behaviour doesn't occur, and I used to get that message
all the time with an earlier version of KMail that never exhibited
the message-selection problem.)

Operating system: FreeBSD 4.5.