KB Article: http://support.microsoft.com/kb/974070

INTRODUCTION

Consider the following scenario:

  • You share an .xls file and an .xlsx file in an offline folder on a file server that is running Windows Server 2003 or Windows XP.
  • You open the folder in Windows Explorer from a computer that is running Windows Vista.
  • You edit the .xls file, and then you save the .xls file to the offline folder.
  • You open the file from another computer.

In this scenario, you find that the changes to the file were not saved.