I have been having the same problems...
I am using a Compaq Presario 1900T laptop and running Knoppix 4 with kernel 2.6.12. I have tried Ubuntu 4 and 5. I have tried Mandriva 2005 LE, RH9, FC3, FC4, Debian Sarge, XandrOS, DSL 1.4, DSL 1.5, Puppy, etc.
During startup, I get this error every time (unless the system hangs, then I get nothing)
Shortly thereafter, I get an error after "Starting hotplug subsystem:
The text moves so fast that I can't seem to copy it down fast enough. The amazing part is that the snd-nm256 loads successfully at the end of the hotplug subsystem. To make matters even more confusing, none of the window managers will load except Gnome, and only if I log in at root using the console login option. Root cannot startx kde, which is my preferred wm. I have tried logging in through the GUI, and I have selected almost all of the available windowmanagers, to see if they'd work.
So, once I'm logged in as root, and in Gnome, I still don't get sound. I have followed the instructions listed above, and when I try to do the ./configure;make;make install for both the alsa-libs and alsa-utils, I get a disk space error. I don't get it. There is still plenty of space on the partition.
lsmod | grep snd
snd_nm256 69600 0
snd-AC97_codec 72312 1 snd_nm256
snd_pcm_oss 47264 0
snd_mixer_oss 18304 1 snd_pcm_oss
snd_pcm 77316 3 snd_nm256,snd_ac97_codec,snd_pcm_oss,snd_mixer_oss,snd_pcm,snd_timer
snd_timer 23556 1 snd_pcm
snd_page_alloc 11268 1 snd_pcm
snd 46820 6 snd_nm256,snd_ac97_codec,snd_pcm_oss,snd_mixer_oss,snd_pcm,snd_timer
soundcore 11104 1 snd
gives me nothing.
alsaconf sure looked promising, until at the very end, when it told me that there were no sound devices. It saw the nm256 and configured it, but then reported thatit was not present?
WinXP has no problems with the sound card, and sound is the only reason I have not completely wiped XP from the laptop's hard drive. I have reinstalled, and I still don't have any luck.