My Windows 7 (64 bit, Dell) computer seems to randomly pick when it wants to play sound and when it has better things to do. I upgraded the soundcard’s firmware and tried all sorts of things but could never make the problem go away without having to reboot. Tonight I found a way to get the sound back immediately.

1. Right click the speaker icon.
2. Click “playback devices”.
3. Double click “S/PDIF”.
4. Click “Supported formats” tab.
5. Click on the word “44.1 kHz” to select it (not the checkbox, the word itself).
6. Click “Test”.
7. You then get a warning box.
8. Click “Yes”.

Source: memolipd on m-audio forums.

I tried it tonight and my sound came back right away. I’m not sure if this will end up being a permanent solution or not. I will update this post if I find that it doesn’t have a lasting effect.

Not a permanent solution, it seems. Sound disappeared again the next time I turned the computer on. The good news, I guess, is that this trick worked to bring the sound back again.