I was working on a song, and suddenly the audio output stopped working.   One of the audio buses had its volume maxed, but nothing was being sent to the sound card.  Restarting playback didn't help.  I had to close and restart SONAR to get the audio working again.
 
Has this happened to anyone?  Is there a faster workaround (like a "reset audio" button) or a way to prevent it from happening?

Hit the audio engine reset button in your control bar.
 

Also, if you've been using an external audio player, to e.g. play a rendered WAV file, that will prevent Sonar to playing. Sonar seems to not attempt to re-acquire the driver. I've found that loading preferences, click "Apply" (with NO changes), fixes that particular problem.
 
 

I experience that too, not very often but quite annoying. Nothing helps, only complete reboot.