PROBLEM:
Removed Windows 7 computer from domain and into workgroup. After that unable to add back to the domain
SOLUTION (in this case, this is not a standard solution):
Disable IPv6 and after reboot enable IPv6
Click here for instructions on how to disable IPv6 (How to disable certain Internet Protocol version 6 (IPv6) components in Windows Vista, Windows 7 and Windows Server 2008)
