ManualObjects not being lit

I have a light and some ManualObjects, which are textured quads, in my scene, and the light doesn't affect the ManualObjects at all.
the material that I am using for the quads:
material Terrain/Sand
{
technique
{
pass
{
texture_unit
{
texture Sand.jpg
}
}
}
}

I can see the quads when I turn on ambient light, but I want lighting effects.....

By definition ambient lighting is not affected by actual lights in the scene. Try adding a diffuse lighting value to your material.