I have my new iMac hooked to my television via mini display port with hdmi adapter, and an optical audio cable from the minijack port. These are connected to a Bose receiver. For some reason, sometimes the sound will not work. I am usually watching things from itunes, avi files, or videos from internet sites such as NBC, etc. Sometimes it works right off the bat, but other times, no matter how much I mess with it, the sound will not work. Occasionally changing the sound settings (built in digital out, to built in hdmi out) will kick it in, but it is not consistent at all. Usually I have to quit and restart my player (vlc, itiunes, and quicktime are the ones I use the most, turn the receiver off and on, mess with the settings, and eventually it works, though never from the same attempted solution. Help?