I've found that backing out the patch "ppc64: improve g5 sound headphone mute" at
http://www.kernel.org/git/?p=linux/kernel/git/bcollins/ubuntu-2.6.git;a=commitdiff;h=4be8dc7ff69182610b40a078b9815bcdf27e0c49
makes sound work on my iBook again.
I've found that backing out the patch "ppc64: improve g5 sound headphone mute" at
http:// www.kernel. org/git/ ?p=linux/ kernel/ git/bcollins/ ubuntu- 2.6.git; a=commitdiff; h=4be8dc7ff6918 2610b40a078b981 5bcdf27e0c49
makes sound work on my iBook again.