Someone here can probably give you a more specific answer. Meantime, I can point you in the right direction.
By default, during installation, Office creates an installation source directory. You can disable it by choosing to 'remove files used for installation'. When a new user starts Office, access is required to this directory. This directory can be network hosted if required to save space on your clients.
I'd guess there are two or three possible scenarios which would lead to this message.
This page and the links from it should allow you to determine and resolve the isssue.
Let us know how you get on.
Thanks,
Xan
Message Edited by Xan Todd on 06-01-200711:04 AM