For my system, the problem has been cured by the recent update to the kernel: I am now running
Linux ubuntu 2.6.24-17-rt #1 SMP PREEMPT RT Thu May 1 16:23:33 UTC 2008 i686 GNU/Linux
and the sound device (VIA 8237) is now correctly recognised and both ALSA and pulseAudio servers generate sound.
For my system, the problem has been cured by the recent update to the kernel: I am now running
Linux ubuntu 2.6.24-17-rt #1 SMP PREEMPT RT Thu May 1 16:23:33 UTC 2008 i686 GNU/Linux
and the sound device (VIA 8237) is now correctly recognised and both ALSA and pulseAudio servers generate sound.