I do have an idea on this:
It may be that you have not set up a favorite river list. Since James changed the homepage to show your favorite rivers listed when you are logged in with your user name, if you dont have a favorite river list made you may be getting an error. If you log out and then look at the home page do you still see the error and no rivers listed?
That is my idea, but I am no programer like James, just a challenged hacker...