I had the same issue.
What I've done:
- Added a general user as administrator and logged in successfully
- Added a new (active directory) group and gave it administrator permissions
- Logged out with the general user
- Made myself member of the new group and removed my account from the old group.
- And I could login again with my own account
- And of course I removed the general user
What I noticed was that I can't remove the old group, keeps saying that it can't find the group (DOMAIN.LOCAL\VC-Admins).
When I change permissions it creates a new group (DOMAIN\VC-Admins), after that I can delete the newly created group but still the old one exists and cannot be removed?