For some time now with the late version 7 of Avast! and new version 8 of Avast!, my NCSI (Network Connectivity Status Indicator) across all tested computers stops working with Avast Web Shield scanning defaults. I found the solution to my problem here:
http://forum.avast.com/index.php?topic=84506.msg686860#msg686860
Which was to enable the following:
Avast main GUI → Security → Web Shield → Settings → check “Scan traffic from well-known browser processes only”.
Then save, reboot and NCSI is working again as it should (yellow exclamation mark in Windows 7 disappears, and in Vista the internet globe appears).
Alternatively I tried additional ways to resolve this issue without checking “Scan traffic from well-known browser processes only”. I tried to exclude http://www.msftncsi.com/ncsi.txt along with wildcards with no luck. Only after I excluded svchost.exe which initiates the Windows Location Awareness service was I also able to resolve the NCSI issue.
Hopefully this brings some attention to the issue and a permanent resolution.