Can you attach a screen shot of what the stroke looks like (using the "Manage Attachments" feature of the forum, which is found underneath the posting window)?
It could be that you might need to add the "no_ink.inf" file workaround, which some tablets need to interact with ArtRage correctly. To try it out, just create a new folder in your ArtRage "Resources" folder (on Vista, it would be here: c:\program files(x86)\ambient design\artrage 2\resources\) and name this folder "no_ink.inf". This folder only acts as a trigger for ArtRage, so nothing needs to be in it. When ArtRage opens, it will find the "no_ink.inf" file in it's resources folder and understand that it needs to ignore the ink services being used by your computer.
Nothing is easy to the unwilling.