Left headphone speaker goes out

Hey guys. I have a custom built computer. Plenty of ram, nice video/sound card, etc. When I plug in my headphone set into the front jack of the computer it will work fine. After about 10 or 15 minutes of listening to music the left speaker of the headphones will start to make a crunching sound until it finally goes dead and only the right speaker of the headset works. Sometimes the left speaker will come back on and sometimes it wont. If I restart my computer they will work fine again for a little while but then the left speaker will go right out. I have tried many other pairs of headphones and get the same result. I notice that if I go watch a video on youtube, the left speaker will click back on and as long as the video is playing it will stay on. Any input or advice would be much appreciated. I run Windows Vista basic home and the program I use to listen to music is the latest version of windows media player.