When the Network Shield on Avast 7.01474 is active on a Windows 8 machine, one is unable to properly navigate or load the user interface for routers. This has been noted on chat forums (including this one) going back to Nov 2012. And still nothing. I am unable to load the Asus, Verizon (Altec?) and Linksys router interfaces with the Network Shield active. It doesn't matter what browser I use. Disable Network Shield and things work normally again.
The reason you have not heard a ton of complaints is because Windows 8 is slow to be adopted AND how often do folks login to the router interfaces via a web browser? This is a problem, please fix it.
