Vista permission issue (user/computer specific)...?

There were a lot of way I could go with this, but my searchs did not net me
with a result. If there is a thread that touches on this issue, please direct
me to it. In any case, her is the 411...

Office network (Windows Server 2000-Active Directory, Windows Server
2003-faxing program, client computers running Vista Business). Keep getting a
DCX output error when the Vista users attempt to fax, but check out these
results:

1. The DCX issue appears only when the users (1, 2) sign on to their OWN
computers.
2. The DCX issue DOES NOT occur when user 1 signs on to user 2's computer
and vise versa.
3. The DCX issue DOES NOT occur when any other user sings on the 1 and/or
2's computer.
4. The DCX issue DOES NOT occur when users 1, while using its own
computer, right clicks and selects "Run as Administrator" (inputting the
username/password of the network administrator). Same for user 2.
5. This DCX issue DOES NOT occur when users 1 and/or 2, while using their
own computers, have their network privileges elevated to Domain Admin status.

I just don't get it. All I can surmise is that there maybe a program,
installed by users 1 and/or 2, that is causing this. Any help would be
appreciated.