Backup Selections shows *some* remote folders as empty

This is killing me.

In the Backup Selections tab, two critical folders show up as being empty
when viewed through the administrative share (D$).(They are NOT)

- Other folders are perfectly normal - through the same share.
- All folders are visible through a user share (in BE).
- All folders are visible through D$ using windows browsing or NTBackup from
the same backup server.
- Tried both with and without the Remote Agent; no impact.

I don't think the following is related, but in the interest of full disclosure:
The machine involved is a W2K PDC emulator and RIS server (this is a SIS
drive), and these 2 folders are shared directly and advertised through DFS.
...

- Running a backup on these folder works sometimes, sometimes not - Sometimes
one works and not the other! There is never an error; it simply doesn't back
the folder up. The only way I can tell is the amount of data backed up and
whether they show up in restore selections.

Sorry:

BENT 8.6 build 3878.

I guess I was really asking: does anyone know how the 'Backup Selections'
tab GUI is populated with available folders and files? I would have thought
that it would have used Windows Explorer, but as I said, direct use of Windows
Explorer does not result in the same problem. I kind of suspect a permissions
problem, but I don't know where to look; BE is running as a Domain Admin,
as am I.

This turns out to be a DFS related issue.