Did you know that when you add a new Active directory user as a  Windows Login in Dynamics NAV 2009 SP1 in an environment where Windows server 2008  and SQL server 2008 are installed , the new user is automatically created in SQL server Login? This means that we do not have the issue of manually creating SQL login  for Active directory (AD) users. All that is required appears to be logging  into Dynamics NAV as a Super user and then adding a new AD user to Windows Login and synchronise permissions.

Note: I used Windows server 2008 Enterprise and SQL server 2008 - latest service pack installed on the same box in my test.