Vista - resorting search results generates a new search

When I do a search of my Indexed Locations, the results display with the
following column headings - Name, Date modified, Type, Folder, Authors. When
I click on any one of these column headings to simply resort the search, it
appears that the search tool is performing the search again (the green
progress bar reappears at the top and creeps left to right and my new sort
does not appear until the green bar is finished). The process of resorting
the results is extremely slow. I would think that a simple resort of a
search would be instantaneous. Is there something that I have
mis-configured? Thanks.