I just upgraded from the free 4.8 to free 5 (Vista Ultimate x64), now I can’t connect to web sites using any of my browsers unless I stop “web shield.” I tried the suggested solution of using the V5 uninstall tool and performed a fresh install of v5, but the same problem comes back. My sister is having the same problem, which she thought was a problem with her Blackberry being unable to update it’s software. If I knew version 5 wasn’t ready for prime time I would have left 4.8 on. The “obsolete” popup for V4.8 was premature.
To the best of my knowledge, Avast! cannot block internet access.
What is your firewall?
Barring a conflict with your FW and the web shield and its proxy function, here is another possible source of problem/solution>>http://forum.avast.com/index.php?topic=57443.0