Msc slow and not responding

I had issues with 3.1 so I uninstalled it and then installed the latest version. Same problems involving very slow start-up and actions, not responding to actions and 'not responding' messages. Playback bar isn't tracking correctly. Oddly, my old 2,3 works better. The problem started with audio/port audio issues. Tempted to reset windows audio to default and reinstall 3.4 again. Any suggestions. (I have all my scores, styles, soundfonts etc saved)