What causes the screw modifier to fail and create black 2d slice from a bezier curve? I am trying to create a plate using a Bezier curve as the profile then use the screw modifier to create the full outline as in this video tutorial, when I apply the screw modifier to the curve that I have created it makes a black 2d horizontal slice instead of the full 3d plate outline.

This shows the bezier curve I have drawn

This shows what happens after the screw modifier is applied
I tried using a line drawn with Nurbs Curve and was able to apply the screw modifier to create a 3d object.

I am not sure what it is that I am doing wrong, any help that you can give will be greatly appreciated.
Edit -
I suspect you've scaled the curve to 0 in one dimension or another, in Object mode, to flatten it. If the object carries that transform, it still will, after being modified. Ctrl A &gt; Apply the scale of your curve.
Think twice, every time you scale in Object mode during modelling. Prefer to do it in Edit mode.