Can't open excel file

[D. Spinner]

If I try to open an Excel file from the My Documents
folder, an error message pops up. 'Windows cannot find
c:\My Documents\folder name\file name.xls'. Make sure you
typed the name correctly, and then try again.

If I open Excel and try to open the same file, it will
open.

If Excel is open and I try to open the file, the same
error message popos up.

Is there a known solution for this problem?