black renders

Spud

Hi All, forgive me if I have posted this in the wrong place, I am a complete newbie. For some reason my renders were rendering black in 3delight, no matter what I load into the scene from the content manager. I decided to load a scene that I created a few days ago, and it rendered fine. When I went back and tried to render another scene I loaded from my content manager it started rendering white. It is driving me mad. Can anyone please help. Thanks in advance.