Backing up NAS - only public shares available..

[C_B_4]

We have a Buffalo Terrastaion on our LAN which graphics files are stored on from our Mac department.  I followed the document on Symantec's site about adding a "User Defined Selection" and I can see the public shares fine.  When I attempt to go to a share that has an ACL defined, even though I'm using a known good account on the NAS box, I keep getting "Access Denied."  I'ved used: 

username | password
(IP of NAS)\username | password
{NetBIOS Name of NAS)\username | password

Any help for this solution?  We must have the ACL's in place.

[Ken_Putnam]

Have you tried creating a user with the same name and password as the Service Account on the Terrastation?

Is there any way to use Domain IDs rather than local IDs for your ACL?