I just wondered about why i couldn't login as member of the domain administrators group to the SQL-Server after i added this group to the SQL as sysadmin. If i add me as user itself the login workes fine. Here is the right "procedure":
- Add Domain Admins group in the SQL Server Security Login
- Give Sysadmin rights to the Domain Admins group
AND (if you login as member of the group)
- Disable UAC or start the SQL Server Management Studio as an Administrator
