This section contains explanation on some of the user source problems.
An error occurs after adding an administrator group from Active Directory, when the AD is linked to the AD Root Domain
Open %SystemRoot%\system32\drivers\etc\hosts in a text editor.
Add the <IP-Address-of-the-AD-Server> <Domain-Name> entry to the file.
For example, you could add the 164.99.165.51 sussex.nhs.uk entry to C:\WINDOWS\system32\drivers\etc\hosts, where 164.99.165.51 is the IP address of the AD server and sussex.nhs.uk is the domain name.
Open /etc/hosts in a text editor.
Add the <IP-Address-of-the-AD-Server> <Domain-Name> <Short-Hostname> entry to the above file.
For example, you could add the 164.99.165.51 sussex.nhs.uk sussex entry to /etc/hosts, where 164.99.165.51 is the IP address of the AD server, sussex.nhs.uk is the domain name, and sussex is the short hostname.