Error 405 means that there is a connection problem with the Portal Gateway and the server. Double check the following:

-User Name & Password (Make sure user is an admin)

-If user is associated with a domain make sure the domain is specified in IIS (see related questions)

-IP Address

-Disable all firewalls including Windows (see related questions) 

-If IIS was installed after .Net make sure ASP.Net is registered with IIS (see related questions)

If you added a new instance to an existing SQL make sure the permissions are correct (see related questions)