I'm going to venture a guess and say that this Linux version doesn't support the changes made with the way Visata and 7 access network drives and shares. I have a network of 20 XP workstations and they can access the drives using active directory authintication without issues. However, when I was setting it up on my Windows 7 machine I couldn't access anything after I set permissions using AD user accounts.
I didn't have a problem with the NAS AD-authenticating actual individual user accounts; the problem was with the default "Domain Users" and "Domain Administrators" groups.
Now that I've upgraded my SBS 2003 system to SBS 2008, the NAS no longer joins the domain since the version of Samba WD uses does not support 2008 AD. So I've got a useless NAS. I've since added another vendor's product (I'll post that in another message so if it's deleted by moderators, this message won't be affected) and that Samba does have the appropriate support although I have not officially added it to the domain nor am doing AD authentication.
I'm waiting for the next software update from WD to see if they'll fix the issues.