Make sure you have 3.5.11 if you are using Mavericks.
Find this by pressing Ctrl + 1 or going to Help > About ArtRage
ArtRage Studio & Studio Pro Support for OS X 10.9 Mavericks
While the current version of ArtRage 4 works with OS X 10.9, the older Studio and Studio Pro versions do not work correctly.An update has been released to address this problem and you can find details in our forums in this thread – OS X 10.9 Mavericks – Studio & Studio Pro 3.5.10 Update.