I have a mid-2010 17" Macbook Pro and recently I have been having issues with the sound when I have it connected to my stereo system. I use an toslink cable. The sounds keeps cutting in and out and it is very annoying! I have tried everything I can think of to fix this issue and I am not having any luck. Through a clear ring on the cable I can see that the red light is staying on, so it isn't the signal that is intermittent. I found somewhere online that going to library/preferences/audio and deleting the two .plist files there would fix the problem. A few weeks back I was having an issue where the digital audio didn't work at all and deleting those two files fixed that problem, but it does nothing for the audio when it keeps cutting out. The sound works beautifully if I use headphones or the built-in speakers. I only have the problem when I connect it to my entertainment system. Does anyone have any suggestions on how to fix this problem?