I had the same problem. I was connected but oddly could not go to many sites, mostly secure ones. Problem persisted in both IE and Firefox.
I finally recalled when the problem arouse. Right after I installed Norton.
You cannot remove Norton through traditional ways of uninstalling. Open your Norton Internet Security. On the bottom left panel you see the user accounts, click on it, enter login as Supervisor, and if you have never logged in, leave the password area blank, and hit enter. Then go to your control panel and Add/Remove programs.
Choose Norton Security and "Change" option. You will see 3 choices. Choose, Remove Norton.
Once its done, restart your system, and see if you have any other Norton or Sympatico programs. Uninstall them through the tradditional way. Restart again and Vioala! You are back in the game with no problems.