I've seen the symptoms many times, with EditPythonPrefs and PythonIDE (not 100% sure about PythonInterpreter), but mostly under 10.1.x (as I haven't been using MacPython all that much yet under Jaguar). It always helped to zap the preferences, although I don't recall whether it was "official" Python prefs file or the .plist. I'll keep my eyes open and experiment a bit. Just