I built my world following the guidelines, but when I start up my game, it closes to an error message saying it failed to load the objects. It loads fine with the sample.world, but not with mine. The files are there, and I saved/built the world. What am I doing wrong?

maybe you don't set the same path (IOPath) that you set to World Editor at program startup (plus, the World Editor doesn't check for errors, so if an object is missing it will work ok, but in game codes you need to make sure that everything is setup properly)