I recently setup a projector mount, and ran 100 ft. of shielded Cat5 between the DVD player and the projector. On both ends of the Cat5 are video baluns to convert Cat5 to composite video. Btw, this is an auditorium setup. So when I plug up the video it works fine, but the moment I plug up the sound from the DVD player to our mixer board the picture garbles up and the projector loses the signal altogether. I've isolated the problem to the connection to the mixer board, because I can hook up the sound to the input of a keyboard (musical, not computer) and it works fine, but if I then connect the keyboard to the mixer board the picture disappears again. I assume this is interference, and I've read that with shielded Cat5 (STP) I only need to ground one end of the cable. Is this correct? I have both ends grounded now (connected to shielded RJ45 connectors), so could this be the problem?