Default Headphone jack problem - mic not working

Hi all,
I got g2x from my friends to use temporarily. I tried various earphones like skullcandy, Iphone etc but none of the mic seem to work. When i connected my ep 630 which does not have mic, the phone's default mic is also not working. This is very annoying as i could not attend a phone call with earphones plugged in and could not buy a compatible earphone with mic either.

Please help guyz !