Update to 10.6.8 broke my optical audio…: Apple Support Communities. So it appears that using Time Machine and restoring an older system file fixes the issue. Jan helpfully explained how to fix this.
Hi shorafix, you can find appleHDA.kext in Macintosh HD/System/Library/Extensions/AppleHDA.kext
just select it, start timemachine a restore old kext from date when you have 10.6.7 installed..