If you receive this error message upon accessing Microsoft CRM 4.0 for the first time after an upgrade, chances are you are simply using the wrong URL. It is important to note that because of the new multi-tenancy feature in CRM 4.0 it is now necessary to reference the Organization name in the URL. The correct format for the homepage for example is:
http://servername:5555/organizationname/
As always, if you are looking for professional Microsoft CRM Consulting for assistance with installation, migration, or upgrade, contact Kazmarek Technology Solutions directly.