But, when ugradeing from 4.7.817 to 4.7.827, this causes my WIFI connection to fail.
Were there any warnings when the wifi connection failed ?
What is your firewall ?
Does it allow ashWebSv.exe internet access.
I haven't heard of any wifi issues associated with the 4.7.827 release in the forums (I don't use wifi so I can't help in that direction). I don't think that there was anything in the latest release that could effect the wifi connection.
Worst case scenario I would suggest a clean install of the latest version.
Download the latest version and save it to your hard disk, download the avast! Uninstall Utility,
find it here and save that also.
Uninstall using add remove programs, reboot, run the Uninstall utility, reboot, install the latest version, reboot.