I tried to make an animation, in which a lamp moves along a path, lighting some text.

The text was made with the text tool and then I used the BevelPlus tool to get it in 3D. When I render one frame, I get the text and the lamp, as it should be, but when I render the movie the text has disappeared.

When I close Maya and open my scene again, the text has disappeared, but in the outliner, all objects are still there.

Does anyone know what's going wrong?