While migrating pastium over to MongoDB (from CouchDB), I found [a] snippet in the routes.php file [that makes it so] when the user enters the application via the root url (/), he instantly gets redirected to /pastes/add (or a different URL if you have custom routes configured). This may seem ok at first, but there's a problem. It doesn't take URLs into account that don't live directly under the document root.
The snippet he references and others showing how to correct the issue are included - replacing the location array controller/action information with the static class information for the route in a match() call. For more information on the routing in Lithium, see these manual pages.