This most likely occurs when you first switch from demo mode of a new installation to production mode. The first time you do that switch, the production database has to initialize and depending on the speed of your server, sometimes the database process can take longer than the IIS process.
You end up seeing a header menu like this when you log in:
To resolve, log out and log back in, the database should be set by now. If that doesn't resolve it, restart IIS and then log back in.