As idenfied, the problem that you are experiencing is that you do have interenet connection but you are unable to open any web page. Well this might be resulting from different issues. There was previously a bug that was idenfied causing this trouble in Sevice Pack 3 and in order to get the problem solved, you will be required to get to the below address:
Still your firewall might be causing the trouble. You should see if the firewalls is not restricting the blocking the connection or still the browser isn't being allowed to get to any website without the firewall activated.
Also please provide the information about which anti virus application you are using and if it is a trial so that we can provide you better help.