So the internet traffic between the Router and Your machine is good - but some software in the machine itself (firewall) is preventing the final delivery of the packets of data to your browser.
I don't know the answer but to find out what application or process may be causing it (so that you can stop that application or process) I would begin by using the machine's Task Manager.
I would also "kill" everything in the start-up list as a diagnostic - but make a note of everything killed. I would probably do this first.
Good luck...
Peccavi
March 2010