Window can't communicate with the device or resource

I use a Toshiba laptop 32bit, the internet was fine until I got the message "Window can't communitcate with the device or resource (primary DNS server)". I checked the wireless network connection, it shows CONNECTED, and has Internet access but I can't go online. Anyone help, please! I tried to flush DNS but still not working. So frustrated for 6 months already.:mad: P/s: my friend's other...