well, that is a strange problem, that I'm sure not many people have come across. What do you think? People single you out and don't answer your posts? you gonna cry about it? bitch more?
seriously, chill out, that attitude isn't gonna get you any help.
as far as your problem is concerned, that 5v pin at the top of the board is pretty close to the a/v output plug if I remember correctly. Maybe you lifted the connection between that 5v pin and the audio or something. I'm not really sure, its a wierd problem. if you're desperate and don't mind being a little dangerous, try booting the xbox with everything pluged in, but the dvd drive off to the side, so that plug is exposed. Then while you know sound is playing, push on that pin a bit to see if it does anything. I dunno, just a suggestion. just looking is a very poor way to judge a solder point. try a multimeter or something.
anyway, your welcome, and try reworking that attitude a bit. good luck