Apple’s latest Snow Leopard update seems to be wreaking havoc with audio out through the optical and HDMI ports on the Mac mini.
According to Swedish Mac blog Allt om Mac, many users who use their Mac minis as home media centers are experiencing the issue since the 10.6.8 system update, which causes audio to drop out completely on a regular basis. Only a complete reboot will restore sound again.
A thread on the Apple Support Communities forums is beginning to gain some length as more and more people report their issue, which Apple is apparently aware of.
I’m sure they’ll be an update to rectify this, but whether it drops before Lion or not remains to be seen.