heya; when you are working on a scene, there is an option for showing ground shadows. these arent REAL shadows, it's just a projection of the silhouette onto the 'floor' so you can see where your model is. if you want the lights to cast a similar shadow, you need to turn on the groundplane for them to cast the shadow ON. okie? :) (or, you can save the unrendered scene and composite the ground shadow with the rendered scene, if you like.)