Bought new laptop, so no other protection software installed beyond windows firefwall, and did a clean install of Avast 7 (free). The Web Shield blocks all browsers, disabling the Shield removes the problem. I have a pc, on the same network, running Avast 7 with no difficulties. Any advice?
Try a repair of Avast.
Are you positive there’s no trial AV as nearly all new systems come with one ( Norton, TrendMicro, McAfee ), even if not activated it can still cause issues with avast.