For what it's worth

Suddenly, out of the blue, files on a DNS-323 started reporting problems like:

Unable to save permission changes on [File name]
Access is denied

You don't have permission to open this file
Contact the file owner or an administrator to obtain permission

Error applying security
You require permission from Unix User\nobody


The cause seems to be related to editing a file in Vista (see forum discussion).

The workaround that limped me through:

Using the Easylink utility, DELETE any existing Mapped Drive for the PC you are working from.

Using the Network Access within the Configuration options, add a new "All users" mapping of the problem folder (tick-box for All Users rather than "User" or "Group") . Map THIS folder for your user using Easylink - and you will find that you CAN now open your files.

Remember to remove the all-users access to the folder if free access is a problem.

Conclusion on the DNS-323: too many hidden nasties to be a reliable choice.  I was within a few minutes of having to install "fun_plug" and learning how to modify permissions using telnet - not the sort of administration level promoted in D-link's promotional material. And whilst similar problems have been documented for over two years, D-link seem to have been in no rush to fix things. Avoid.