For the webboard login, check the cookie settings in FireFox.
Cookies from the webboard/avast ID need to be accepted.

The 10 february update is not the latest > https://forum.avast.com/index.php?topic=197955.0

WPFFontCache_v0400.exe
That is part of the .net 4 framework.
You can try this to see if it makes a difference :

  • Stop the WPF Font Cache 4.0 service.
  • Delete all of the WPFFontCache_v0400* files. Likely they are in: C:\Documents and Settings\LocalService\Local Settings\Application Data\ folder.
  • Start the service again.

wuauclt.exe
Disable the service and see if it makes a difference.

As you are on DSL, chosing for one of the dial-up settings is wrong.
There is a permanent connection with DSL (consider it as being on a network)