[support] 4.6.5 to 4.7RC3 upgrade: successful, but front page is default until users log in

[Tim Vaughan]

I upgrade from 4.6.5 to 4.7.3 and it seems to have been successful. 
However, visitors to the site see the default message:

"Welcome to your new Drupal-powered website. This message will guide
you through your first steps with Drupal, and will disappear once you
have posted your first piece of content."

This message disappears when users log in.  It does not disappear when
I post content - the content appears as normal but, on logging out,
the default front page appears again.

How can I make Drupal realise that it's not a new install?  Is there
an entry in the database somewhere that I can edit manually?

Thanks,

Tim