You're talking about OS 9 startup, not in Classic, right? Because Toast won't see anything in Classic, or at least it won't write. I suspect the problem is not OS X, but perhaps you installed newer versions of Disc Burner or Authoring Support, which break Toast compatibility? If yes, disable these extensions, restart and see if the drive is seen. If not, try reinstalling Toast, and plugging in the burner (powered on) with Toast open, and click the bottom of the window where it says No Recorder Found (Toast 5).