[away3d] camera.screen broken?

[mc]

trying to get the 2D coords of a 3D Object using view.camera.screen
(3dObj)

for some reason this doesn't work for me

I get the error:

TypeError: Error #1009: Cannot access a property or method of a null
object reference.
        at away3d.cameras.lenses::ZoomFocusLens/project()
        at away3d.cameras::Camera3D/screen()
        at Basic_Globe_fla::MainTimeline/onEnterFrame()

line of code that produces the error:

var screenV:ScreenVertex = view.camera.screen(sphere)

have tried to give it a dummy Vertex:

var screenV:ScreenVertex = view.camera.screen(sphere, new Vertex())

but error is the same

any ideas what this could be?

Many Thanks