edit user rights via LAN

Hello,

When I connect to our W2K3 server (standard) with admin rights from an XP
PRO machine over the LAN, I cannot add or edit user rights to the ntfs
security list
(right click on folders or files\properties\security) If I do the same task
locally on the server (via the same account) it works fine.
More precisely the User accounts are yet created on the server, I'm not able
to edit the list fore each file or folder remotely.

How can this be solved?

All help appreciated,
Perry