If you forget the trailing slash on the codebase property, or if the class files can't be located at the source (they aren't really being made available for download) or if you misspell the property name, you'll get thrown a java.lang.ClassNotFoundException. This exception will be thrown when you try to bind your remote object to the rmiregistry, or when the first client attempts to access that object's stub. If the latter case occurs, you have another problem as well because the rmiregistry was finding the stubs in its CLASSPATH.
Write once, run anywhere, because there's nowhere to hide! - /. A.C.