更新1:
Just moved back to my room and even the three unknown networks shown are gone and no network is shown in the list. I've been using the 3 routers in this house for almost 4 years. It used to connect just fine via whatever router but recently I started having problem connecting to different routers. Right now I'm connecting my laptop using Ethernet connection. Checked my DCHP settng and it says enabled. FYI the wireless card of my laptop is Qualcomm Atheros AR946x. Please advice. Thanks a lot!