I just bought a 15" MBP last week and got a few apps installed on this machine. And now it looks like I have a problem with the sound. When I use the built-in loud speakers, it is totally fine. But when I plug in the headphones. The left one is bigger than the right one. I check the sound configuration, the balance is put right in the middle (for both built-in loudspeakers and headphones). Therefore, I have to put it 3/4 on the right for the headphones. But I just don't know what is happening with my MBP. Please help me, I believe probably there are some conflicts between the installed software with the drivers or something, but since it happens for both Mac OS and Windows 7 (Boot Camp), I guess I was wrong then. I appreciate a lot.