My friend has a Dell laptop. We surfed internet wireless by a router. First he was using windows firewall and windows defender to protect the system from threats. But recently we had downloaded avast antivirus and updated it. If found some detection which was later deleted. The problem now is that after installing avast the wireless internet connection is not working. The page does not open in Mozilla nor in Internet Explorer. I had check my wireless status but windows is showing a strong signal. Only the pages are not opening. What should I do here.