Hi,
I don't know what is going wrong with your config... but i'm a bit surprised by the title of the thread... Samba might be used as a DNS server (i don't really see how but one cannot be sure of anything in this open world), but i think you're talking of domain controler (which is not really the same thing).
Anyway, i shall advise having a look at chapter 3 and 4 of
http://us3.samba.org/samba/docs/man/Samba-Guide/
The above guide is entitled Samba-3 by Example... very good reading concerning interactions of Samba, printing, DNS, DHCP, Domain controller, logon scripts...