I had a problem where I still had a connection (right click My Network Connections, double-click Local Area Connection, note bytes sent and received) but couldn't reach any websites. Found out I could reach google by typing 216.239.39.99 in address bar. Determined that my Zone Alarm firewall was preventing me from using the host names to reach websites. Opened Zone Alarm and allowed programs to reach internet one-by-one until I could reach google by name.