When I check mail in kmail I'm getting errors in the kmail notification area
(the one which appears at the bottom right of the kmail window when you click
on the arrow) saying "Store failed, server replied: A000234 BAD Error in IMAP command UID STORE: in...".

There are many such errors and the number used for the IMAP operation increases
by 2 with each reported error, so it seems that every second IMAP command is
failing.

The server is Dovecot on Wheezy.  With the default level of logging there
are no errors logged to mail.log.

(kmail:2688): Gtk-CRITICAL **: IA__gtk_progress_configure: assertion `value >= min && value <= max' failed

The .xsession-errors file on the client reports many errors such as the above,
I don't know if they are related to this IMAP problem.

I will attach a screen capture of the problem in my next message.

Also I think that in terms of dealing with this problem we need to have more
information on errors (maybe a way of finding out the command which caused the
error) as well as fixing whatever the error is.

I don't think that Dovecot has a problem in this regard, but there is always a
possibility - however I can't properly investigate that possibility without
knowing more about what's happening.  I personally can use tcpdump (and
probably will) but the typical user can't.