Cannot open files found by 'Search'

When I try to open Word or Excel files found by "Search" I get the message:
"Windows cannot find <filename>. Make sure you typed the name correctly, and
then try again." Double-clicking on the file icon in the 'Search' window
results in the relevant program (Word or Excel 2007) opening, but the file
itself doesn't open. However, if I go to the relevant file in its folder and
click on its icon, it opens as expected.

Given that the files have been identified by 'Search', which also lists
their location, I can't figure out what I need to do to get them to open when
I double-click on the file icon.

Any idea what can be done to correct this situation? I'm using Vista
Business and Office 2007 Professional.