Same thing happened to mine but I didnt know what it was at the time. My mechanic swapped on a new stock balancer and everything is fine now. I wish I would have known before hand so I could have gotten something a lot better than a replacement stocker. I hear you on the sound though, its horrible.
when i put my new balancer in, it was rubbing against mine. it wasnt major major and it was kinda tolerable and it finally wore off enough of the corner of the pulley to stop making the noise...if it didnt stop i was gonna grind it off a lil bit but it was fine