Ack - I spoke too soon. Now, at step 4 of 5 (Specify the username and password you wish to use to access PowerCMS. You will have the opportunity to modify this information and create additional user accounts, once you have completed the Installation Wizard.), I can't add an admin user.
ERROR: Failed to save the settings in the database. Please verify your database connection.
I don't understand what's going on at this point. Sigh...