This will relate to your tablet settings in Windows. ArtRage is able to use Microsoft's tablet standard 'real time stylus' by default if it's available and if you have pen flicks enabled in your Windows tablet settings that would tend to cause this behavior. Painter is probably using the older tablet standard, 'wintab'. You can change to using that only like this:
Edit -> Preferences -> Input Device. Uncheck 'use realtime stylus' and make sure that 'use wintab' is checked. Restart ArtRage when prompted to apply the new settings.
If you still have problems, let me know which operating system you're using and what tablet you're using and I should be able to solve the problem for you. I hope this helps!
Resident Bug-Hunter and Support Guy