Go into the Wifi network properties and then TCP/IP properties and make sure the DNS settings say get settings automatically. If you have selected manual settings then put in the proper DNS servers.
If you are commected to wireless bridge then check that DSL modem connected to wireless bridge is powered on (Many times it happenes :D) then check if your DSL connection data is save in its connection settings (may be someone have done hard reset).
Check your internet connection icon in the system tray. Double click It check network properties. There should be DNS IP. If not check your wifi router for DNS settings.