I've upgraded to ubuntu 11.04 and since then the audio stopped working (I was on 10.10 before that).
I'm using a Macbook Air 3,2 and these are details of my audio card:
description: Audio device
product: MCP89 High Definition Audio
vendor: nVidia Corporation
physical id: 8
bus info: pci@0000:00:08.0
version: a2
width: 32 bits
clock: 66MHz
capabilities: pm msi ht bus_master cap_list
configuration: driver=HDA Intel latency=0 maxlatency=5 mingnt=2
It doesn't work either with headphones or speakers.
Alsa mixer doesn't show anything muted and all the volumes are up.