First, check to be sure that you have not set your preferences to create a demo screen saver. Next, make sure that the screen saver was indeed created with the full licensed software, and not a demo.

Mac: "Get Info" on the screen saver control panel and look at the version number. There should be a "c" or a "u" indicating the license version. If there is a "d", this screen saver was created with the demo.

Windows: Get properties on the screen saver installer and look at the version tab. Check the item named License Version; it should list Unlimited, Commercial, or Demo as the License Version.