Zone Alarm
Most peculiar - I have just 'returned' to my XP installation (fully updated and Malwarebytes checked) having been exclusively using W7 for a week or so to find all http sites in all browsers blocked, but https sites open, and other ports like 2082 for my host server ok too. With ZA off all normal.
I now have Windows firewall running. I am assuming a recent Windows update has caused this - anyone else?