There is a black piece of plastic/rubber holding the left and right channel (white and red) wires together. See where yours is at....if its close to the ends that plug into the computer, slide it back far enough so that each channel (white and red) are separated on their own. It may appear that the plug is plugged in but it might be slightly removed from the computer causing the sound not to work properly out of that channel. When the playfield is pushed back in, you wouldn't notice the wire slightly coming out. If you pull back the wire holder and give each channel slack, then it should stay seated into the computer. Give it a try. Like others said, if the sound is working then its probably just a loose connection. Remember, the Ruby Red 75th has a shaker and if the shaker is moving a lot it causes vibrations and could easily have caused this too. Might happen to your monitor....if it cuts out and says no signal but is powered on, its likely a simple re-seat of the DV-I cable and you are good to go. Best of luck. Let us know how it goes.