You can use zip files for the layouts but not everyone does and they might not be designed to run as a zip (meaning the layout.nut isn't in the correct place within the zip). As a test, try unzipping the layout and see what happens.
The screen you are seeing is typical of a layout issue. It could be because it's not designed to be zipped. It could be that your resolution isn't compatible with the layout. It could be due to an error in the layout.nut (which isn't likely if you haven't modified them). If you provide more information like the theme name and your resolution it would be helpful. Also, if you run AttractMode from the command prompt is there any information/errors on the screen once you close AttractMode?