Two different OSs (XP Mode and Win 7) tested on "connection 1" (the one that has no problems in downloading the files) and "connection 2" (the one has problems in downloading the files).
"connection 1" and "connection 2" provide EXACTLY the same results on
http://test-ipv6.com/ ...
bruce_b, Eddy, my point currently still holds (despite it is clear that you don't like this): Avast simply needs to fix this one.
Instead forcing users to play with DNSs, routers, IPv4 vs. IPv6 and other stuff like that, Avast simply needs to provide software which works like all the other software do (and like it was in their version 12); that is WITHOUT tweaking ANY of that stuff...