[Inkscape-user] Tablet - Panning doesn't work with Pen

I have a button on my Wacom Intuos3 tablet assigned to "middle click" with the intention of using it when I need to pan the canvas.

When I hold the button and move the pen, nothing happens. If I hold it and move the mouse the panning works fine. Is there something I can do to fix this?

I'm running XP SP2 with the latest Wacom driver 6.02-1.