When you setup NT groups for SQL logins, one thing that you have to make
sure is that the local group resides on the machine in which SQL Server is
I have seen many cases where people create the group on the PDC and then
try to grant login to that group.
If your machine name is SQL and the domain is SQLDOM and you create a Local
Group in the domain called SQLGRP and grant login to that group it won't
Create a Local Group (SQLGRP)in the machine itself, add domain users or
global groups to that local group, then grant login to that local group.
So you will be granting access to SQL\SQLGRP rather than SQLDOM\SQLGRP.
I'm not sure if you arehaving the same problem, but this is the most common
mistake people make when granting login to NT groups.
Hope this helped