XBOX 360 Mic Problems persist...why!!! why!!??

I've switched controllers, bought a new mic, used wireless and wired....and still while in game, specifically, RB6 Vegas, I am unable to hear anyone. My mic icon shows up and when I talk it lights up...so why can't I hear anyone else? I'm not a newb xbox user...was a beta tester for the original...so please don't tell me something about maybe I've got my mute turned on...What's up...is it a bug.....surely I'm not alone with this problem..