We have WIndows 7 and an Insignia 42" flatscreen w/ 2 HDMI ports. We use one of the ports for a 2nd monitor so we can watch shows, etc. on the TV from the internet. It has ALWAYS played the sound from the TV when we move the window over and just recently it started playing the sound from the computer speakers instead. So video plays fine but now the sound won't come out of the TV, it comes from the desktop speakers. We changed NOTHING. Any suggestions?