My sound card is

0 [ICE1724 ]: ICE1724 - ICEnsemble ICE1724
ICEnsemble ICE1724 at 0xbc00, irq 18

I don't know why a USB device is listed. Could that play a role in the problem.

I added to the modules file snd-ice1724, and when I rebooted the first time
audio was restored. Then, once I shut the system down, there wasn't any sound
anymore.

Here's some additional information:

mike@mike-desktop:~$ aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: ICE1724 [ICEnsemble ICE1724], device 0: ICE1724 [ICE1724]
Subdevices: 1/1
Subdevice #0: subdevice #0
card 0: ICE1724 [ICEnsemble ICE1724], device 1: ICE1724 IEC958 [ICE1724 IEC958]
Subdevices: 1/1
Subdevice #0: subdevice #0