Green Jumper .....AFAIK asus uses blue ones on mobos and i think it got nothing to do with sound ..
anyways refer to jumper section in the manual .....

http://www.thetrailingedge.com/image...-a8n-e-big.jpg

^^ helpfull to cross chk the jumpers locations...may be while unpluging green pin might have damaged (once happened to my frnd mobo in where he lost complete sound device while shifting)