Are you sure you do not have some kind of filter view set?
I ask because if it is only the last item, it may be that if your
preview pane is set to mark something as "read" after 5 seconds
and if you have a "View" filter to show only unread messages
it would appear to "disappear".
To check your view settings:
Open Outlook
Select the Inbox folder
Select VIEW from the menu
Select CURRENT VIEW
Select MESSAGES
Click the RESET button if it is not grayed out
Apply the view.
Did this help?
--
Nikki Peterson [MVP - Outlook]
When I recive messages, Outlook automatically deletes the
last message. I suppose it is some kind of virus, even
though I am using a virus-programme
Stefan