Wifi problem

I bought samsung s7562 duos mobile last week. Wi fi is not working. It showing all available networks.but not get connected keep on scanning and finally says ' authentication error occured" even for open networks. I tried to flash firmware with different firmwares.but wifi prob still same.. samsung service center also failed to give hands for this issue as they said this is very new to us and cldnt do anythng. What can i do ??