An exclamation mark is shown on LAN/Wireless Network connection

Hi veryone! No internet access while using local Area connection, or wireless network connection, although someone else connects to the same modem router via his mobile phone. I have TP-link(300MBps) wireless N USB ADSL2 +Modem Router. Image: http://img827.imageshack.us/img827/3900/nointernetaccesswhileus.png I have tried troublshoting, then I found the broadband modem is...