Comment 1 for bug 400529

I have this problem as well, and it appears to be a race condition of sorts between GDM playing sound and ALSA attempting to initialize. When GDM is configured to play a sound for "Login Successful", the hw:0 PCM device is busy when ALSA attempts to open it. After I've logged in, I cannot get any sound from ALSA. When I open the Volume Control dialog, there is a device labelled "Playback: Null Output (PulseAudio Mixer)". When things are working correctly, this device is labelled "Playback: HDA Intel - AD198x Analog (PulseAudio Mixer)".

The following lines of my /var/log/user.log file relate to the problem:

Jul 28 18:22:19 haven pulseaudio[3372]: alsa-util.c: Error opening PCM device hw:0: Device or resource busy
Jul 28 18:22:19 haven pulseaudio[3372]: module.c: Failed to load module "module-alsa-sink" (argument: "device_id=0 sink_name=alsa_output.pci_8086_269a_sound_card_0_alsa_playback_0 tsched=0"): initialization failed.

When I uncheck the "Login successful" sound in System / Administration / Login Window / Accessibility and logout/login, everything works fine.