Motion 5 graphic question

Hello all, I've just started dabbling in Motion 5 and am having a problem with one of my graphics. As the graphic becomes larger it looks as if it is wavy along the edges. The original file is quite large, could this be the problem? The original graphic is a jpeg. Here is a link to youtube to show what I mean since I can't really describe it. Any help as to what the problem is and how to fix it would be great!

Thanks!

http://www.youtube.com/watch?v=_plgSJYsV48