I have Lenny fully updated on my desktop. It is a fairly recent installation. I had no sound so I investigated, found that I had not installed Alsa, and installed it. I then ran alsaconf. And lo and behold! I had sound.
Then sound disappeared again. I reran alsaconf. No luck. I fiddled with the settings in Kmix. (I use KDE 3.5.9.) Still no sound. I tried to install Alsa again, but it is there. I reran alsaconf. While it was running the white sound coming from the speakers went - and returned when alsaconf had finished. But still no sound. I ran dmesg | grep alsa - and for good measure dmesg | grep ALSA. (I'm desperate.) Both returned nothing.
I have googled. To no avail.