No Sound! 0o

I was watching a movie in VLC when the audio suddenly crackled and cut out. Neither system sounds nor multimedia would make noise. I've now restarted, but the sound hasn't come back. What's weird is that when I adjust the volume there's a null sign below the volume bar (see attachment). Evidently, my computer can recognize sound isn't working, but it can't do anything about it.

What does the System Preferences in the Sound pane say? Any messages in there?

There was a mix-up with some video apps a while back having to do with the Audio MIDI setup.app. These are the settings you should see...

Everything appears to be ok again now... the sound suddenly came back about a few minutes after I posted this. Really bizarre though.

Glad it's working again. Maybe it had something to do with the system's cache somehow that needed time to empty itself.