I had to contact Symantec Support and after 3 days of calls and emails, they helped me resolve the issue! The support rep. first reviewed all the DLO servies running on the server and determined that everything was started. Then we went to the Windows registry:
1) Start > Run > regedit
2) HKEY_LOCAL_MACHINE > SOFTWARE > Symantec > DLO > AdminConsole > User Interface
3) A new DwORD Key is added: New > DWORD Value
3) Name: SelectUserGroupValidate
4) Value: 0
I had to restart the server and I was able to add an user without any issues after that!