Can you tell me the steps you are using to try and move the canvas?
When you say it stops, does it move at all? Does it make any difference if you are at the edge or the middle of the canvas when you try to move it?
Also, does this happen if you start up ArtRage, create a canvas of this size, lay down a couple of strokes of paint, zoom in to 200% then try to move the canvas around? Finally, are you able to move the canvas fine with the mouse, but not with the tablet or does that also fail in the same way? Just trying to understand the details of what you're seeing there. Looking forward to helping you out!