i remember this happened before when i first connected the mini and i found a solution but i cant remember or find the solution. i have a 2009 mini connected to my tv, using hdmi with a (i think) belkin adaptor that takes the optical audio output from the headphone socket and feeds it into the hdmi. its worked for about a year without a problem and all of a sudden, the sound doesn't work. when i go into preferences, its like nothing is plugged into it. even when i unplug it and plug in headphones or usb speakers it cant see them and just says theres nothing plugged in. tried restarting over and over, at one stage a restart showed the optical output, but there was no sound, and the next restart took it back to not showing any output. its a real pain as I'm british and living in portugal so i get all my tv through my mac streaming.