File shows different date/contents from a specific PC/User

All,

I am not a Windows admin, so be gentle.

We have a .xls file out on a mapped network drive (S:) where several people
enter and/or verify contents on a daily basis. It gets updated every day,
including today and has a modified date of 6/9/2016. The drive is mapped
at signon at the domain level.

For a month now, for a specific user on a specific PC, it has shown the
modified date as 5/2/2016. If this user is signed on to this PC and I
start Windows Explorer with "run as administrator" it still shows a
modified date of 5/2/2016. And the information in the file reflects that
it was last updated on 5/2/2016.

I can sign on to that PC as Administrator and the modified date date is
fine at 6/9/2016.

That user can sign on from another PC, the modified date is fine at
6/9/2016, and she can update it just fine.

So it look like it's only that user on that PC.

The PC with the issue is Windows 7 Pro and has been joined to the domain
for several years now. The employee started last November. The problem
just started last month.

I am clueless. Ideas?

Thanks.