SYSCTL.CONF and ECN may be your answer
Search LQ for ECN. I had a similar problem on FC2 Test 1 - I could ping anything, DNS resolved, etc. but could not get a web page to load. I came across the ECN setting for sysctl.conf and once I changed it everything loaded fine.
Never had the problem with FC1 just earlier versions of FC2. Sorry I couldn't post a link - haven't posted enough messages for that. Hope it helps.