Colludium
I think the 'toon' effect that comes with C2 works by posterizing the image and adding a black edge.
I altered some of the parameters and managed to remove the lines....but, when the image is resized
the lines re-appeared.
Have you tried using the 'posterize' effect instead with the level's set to about 8 or 10.
You wont see any lines when you resize.