For people who are upgrading their version of OS X:

ArtRage 2.5.20 has been tested on the latest release of OS X 10.6 and so far we haven't found any problems. When a copy of the release version is made available to us we will be repeating the tests and looking to patch any problems we find, but for now things are looking good and you should be able to continue using ArtRage after the update.