“What Mac OS version do I need to run my new Pro Tools 5.1 update?”
Pro Tools 5.1 now requires a minimum of Mac OS 9.0, though 9.04 or 9.1 is recommended. If you are still using Pro Tools 5.0 or 5.01 you can use Mac OS 8.6. In general we don’t recommend using the “latest” Mac operating system with Pro Tools. It usually takes some time for Digidesign to test all the possible configurations under any new OS. As of this writing OSX, for example, is not supported and we expect a new version of the DSI and DAE will be required (at the very least) for Pro Tools to work in an OSX environment.