Installing NAV to sub-domain server

I haven't used the master domain model, so I'm not positive - but normally in NT domain-level security, you need to add the global group to the local group, not vice versa. IOW, if you want a domain group (global group) to have administrative rights to a local host (workstation or server), you add the global group to the local administrator's group, not vice versa. So, I would think the concept would be the same - you would need to add the master domain global group to the sub-domain PDC administrator's group. This sounds like what you've done, if I'm understanding you correctly, except that you created a separate, new local group instead of using the local Administrators group. But does the local group you created on the sub-domain PDChave administrative rights to that machine? If not, this would certainly be the reason that you can't install software. Hope this helps!