The version of ArtRage on your disk is probably an old version. Some of the older versions have problems identifying the latest versions of the Wacom drivers on some operating systems. To fix this, you need to update to the latest version (2.5.20).
To download the latest version, go to http://www.artrage.com/artrageinstaller.html and follow the instructions there. There is also more information available using the support system at http://www.artrage.com/ar2support.html.