Default [Q] phantom key press s duos

im using galaxy s duos and facing phantom key press .. the touch screen and menu button starts responding itself and the problem is solved after turning the screen off and then on again.. but this problem is very annoying specially during call or sending or receiving text messages..
it all happens on 2g.. on 3g it works fine.. but my problem is this that i cant use my phone in 3g all the time.. plz give a solution of this problem.. i have heard some other samsung mobiles that have this issue.. how many of u face this issue ??

sorry for bad english