I use Poser, Zone Alarm, and a Wacom tablet. They all seem to play nicely together.

I have noticed that sometimes, when you switch between mouse and pen (I use a separate, wireless Logitech mouse, not the one that comes with the tablet), the tablet doesn't recognize that you've switched. First, make sure the Wacom mouse is well clear of the tablet; it won't recognize the pen if it detects the mouse. If it still won't detect the pen, run the Wacom mouse over the tablet a few times until the cursor appears, then remove the mouse and try the pen. That always works for me.