Log out, go to a release page e.g. http://test.musicbrainz.org/release/71af5377-2201-3b81-a5c9-64a59fa1dea7 and click on edit. Since you're logged out, it'll ask you to log in. After logging in, it goes to http://test.musicbrainz.org/release/http://test.musicbrainz.org/release/71af5377-2201-3b81-a5c9-64a59fa1dea7/edit which says "Error message: 'http:' is not a valid MusicBrainz ID"