The headphone jack on my Mac Pro desktop 2007 has given me problems from the start with a loose connection. I kept putting off having it fixed and now when I have taken it in to apple, they tell me they can't find anything wrong. When my headphones are plugged into the jack, the least little bit of movement makes one or both channels cut-out. I have had to jiggle around the jack connection to get it working again. Now, it has caused two different headphones to lose one of their channels altogether even when the headphones are plugged into another source. The headphones were new and worked properly for only a very short while with the Mac. I have the suspicion that maybe the Mac's headphone jack problem may have blown the one channel on the headphones. But, either way, the headphone jack on the Mac acts as if the connection is loose. I have read where a lot of macbook owners have had this problem but I have not found a solution. Someone mentioned that it might be the logic board. Can anyone tell me what it is or how I can get apple to fix it before my warranty expires in October 2010?