Musicians who are thinking about upgrading to version 10.4.9 of Mac OS X should beware that the included new version of auval, which checks Audio Units for programs such as Logic, may reject some of their plug-ins. The auval Audio Unit validator applies stricter testing, and plug-ins which fail its assault course will no longer be loaded by Logic.
If you have already upgraded and are experiencing problems due to the stricter testing, you might be interested in a thread in the Sonikmatter forums, which reveals a way to reinstall an earlier version of auval. Alternatively, by launching the Logic AU Manager from Logic’s Preferences menu, you will be able to put a check mark against any listed plug-ins you want to run, even if they have failed the auval tests. Logic will alert you to the danger of running the plug-ins, but you will still be able to run them.
Some of the coverage of Mac OS X 10.4.9 has been very critical of Apple for increasing the rigour of its AU testing, but which seems a little unfair: faulty plug-ins can reduce the stability of Logic and other AU hosts, so it is right that auval should be improved to test Audio Units as thoroughly as possible; and, as shown, there are workarounds if you need them!