Microsoft has verified the symptom.
If the same file is accessed by two or more users in the same computer, the latest modified time of the saved file will overwrite the rest of the users.
This symptom may occur to some programs, but it does not occur in programs such as Microsoft Word.
For further details, please refer to the following solution in Microsoft's technical support website.
Article ID: Q304789
Last Reviewed: October 18, 2001
Title: Why Data May Be Lost If Two Users Edit and Save the Same File in Separate Logon Instances