When my system gets to suspension while the song being played, and got resumed from the suspension, I found my Rhythmbox player running but no sound coming even from the system. I had to suspend it and press the power button to get the sound back. Why is it happening so?
Try turning off your sound device (click on volume control, click sound preferences, and then go the hardware tab, click the device, and choose off).
Then press alt+f2, and type