Lilolee, it will be difficult to help your father at distance…
If he can’t connect the internet, maybe a firewall is blocking WebShield.
If you can, ask him to check if the following programs are allowed to connect (maybe into Windows Firewall):
C:\Program Files\Alwil Software\Avast4\ashWebSv.exe (avast! Web Scanner)
C:\Program Files\Alwil Software\Avast4\ashMaiSv.exe (avast! e-Mail Scanner Service)