Searching in Outlook 2007

When I undertake a search in outlook, it returns some results but when I then scroll to the bottom of the results and select "Try searching again in All Mail Items", after 2 seconds it returns "No matches found for [search criteria]".  Sometimes it works sometimes it doesnt, so it doesnt make sense to me.  It's as if its not even bothering to search just immediately displays that message.

On a separate note, it sometimes changes the view of the window such that multiple emails from the same receipient is condensed and I need to expand the check box for every sender to see the emails.  What's that about?