We have been investigating a problem running ArtRage 3 Studio or Studio Pro on OS X 10.9 that prevents updates happening on the canvas during paint strokes. I believe we've solved the problem and I have prepared a test build that we need to run by some users before we do a general release. If you are using Studio or Studio Pro on OS X 10.9 please drop us a mail ([email protected]) and we can get you the details of the test build to try. Please include your current ArtRage serial number when you get in touch.