Approximately since I upgraded SpamSieve to 2.8.6, I’ve been seeing problems similar to what’s in this thread. Messages are showing unread in the inbox when they’re not there at all, there are empty messages in the Inbox with no subject, date, from, to, etc., there are occasional duplicate messages, other folders, including Junk Email, show messages, but they can’t be viewed or deleted.
In a similar timeframe, there has been a service pack release for Microsoft Office (including Outlook), so this could be troublesome to identify. Is it possible to get back to 2.8.5 to see if the problem goes away?
In all cases so far, stopping and restarting Outlook has removed the non-messages and cleaned up the display.