samba - Sep 2008 - access denied with ntback and samba shares

Hello,

I am new on this list and I hope, my question is not an FAQ. I did a lot
of searching but could not get the answer:

With ntbackup on a windows 2003 server I try to backup 6 shares on a
server running samba 3.0.24. When I select all 6 shares for backup I get
an "access denied"-error from ntbackup with three of them. Do I select
only those three shares, that generated the error, all works fine an the
shares are backed up.

Where is the source of this problem? Is it Windows, is it ntbackup or is
it samba? How can I get around this error? I would appreciate any help.

TIA,
Christoph Sternberg