Thanks, Sebastian, but I believe my problem is that the "temporary" domain name has not been added as a portal alias.  The database currently running, loaded from a backup of my production site, only has 2 entries in portalAlias, oaklandsymphonychorus.org and www.oaklandsymphonychorus.org. 

I have created an entry in the hosts file on my laptop that has the site's dedicated IP, a tab, and oaklandsymphonychorus.org - I can display the site but I still get the "under construction" page. I can try changing the domain to oaklandsymphonychorus.org.nightshade.arvixe.com, the temporary domain name, and see if that makes a difference; I can also try your localhost suggestion and get a little more experience with my local IIS installation.   But I don't think I'll be able to get the site to load unless someone adds the temporary domain name to the portalAlias table.  I think if we add that in the #3 position it should allow me to open the site for validation.  (Can't be me, I'm afraid; on a shared SQL server I only have read access to the database.)  Your statement, "if the domain name has been added as portal alias," seems to confirm that.