Yesterday I downloaded and installed McAfee's Site Advisor. From that moment I have been unable to access any http sites although my connection is fine for all other connectivity issues including accessing https sites, using e-mail, skype. Even my toolbars are actively fetching info from regular web sites (not secure). It only affects 1 computer in my home network. Doesn't matter if I use IE or Firefox. I've uninstalled Site Advisor. Didn't help.
I followed another thread which suggested that reinstalling TCP/IP will solve the problem. I did this using Microsoft's Guided Help to resetting TCP/IP (only way I found to reinstall (actually reset not reinstall but this may be my issue)). No luck yet.