samba - Dec 2005 - Problem with Samba as Member of AD, Kerberos

Hello all,

    I have this configuration: Samba 3.0.20 as a member server in Win2K3 
AD (runs on Madrake 10.2 - no flames please ;-) ). Winbind works fine 
(wbinfo etc are ok), kinit is ok (or seems ok...), and all users are 
happy...
    Of course there is a BUT...
    All the above work fine as long as I use NetBIOS resolution. For 
example, my server has "XXX" as a name and "YYY" as NetBIOS
alias. When
I access the box as \\YYY\ or \\ip.add.re.ss\ everything is ok and 
authentication is done by my PDC/BDC (both Win2K3) without popups. But 
if try \\XXX\ (as registered in AD and DNS) I get a prompt for 
credentials (which, of course, never get accepted...). The exact same 
thing happens when I disable NetBIOS over TCP for a client and try to 
access the server with any name (from the DNS-only client).
    All my clients are WinXP Pro (except one Win2K) and my 2 Win2K3 DCs. 
I thought I could disable NetBIOS (and WINS on my DCs) as I read that 
DNS in AD is much faster and reliable etc...
    Can anyone point me to the right direction? Or convince me that I 
will not earn much if I disable NetBIOS...
    Hmm, yes, I know... If it works, don't f-u with it but I want to get 
as much as I can from my network (there is A LOT of traffic to and from 
the Samba box).