I have two computers: one XP, one Windows 2000. This problem only occurs on the XP.
The problem: File B is linked to File A using SUMIF formulas. If File A is not open, the File B cells with SUMIF formula linked to File A will return the "#VALUE!" error. This occurs whether I select Update or Don't Update to the "file is linked" question.
The same file works fine on the Windows 2000 computer.