It should not take hours to load new users to CRM. It just sits there "setting up Microsoft Dynamics CRM, this could take a few minutes. I've added many users before with no issues.
Check the active directory and DNS server. May be there are some issues in the communication of the CRM and AD. Also, reset both servers and check the ping of the AD.
Check the active directory and DNS server. May be there are some issues in the communication of the CRM and AD. Also, reset both servers and check the ping of the AD.