Where did you get this avast Pro from ?

There should be no requirement for the update to go anywhere like dl3.avgate.net, updates are usually from http://(without space)download??.avast.com the ?? represents variable numbers.

avgate.net seems to have something to do with avira, do you also have this AV installed on your system ?

Domain Name: AVGATE.NET

Administrative Contact:
Auerbach, Tjark mailto: ?? ?? ?? ?? @antivir.de
Avira GmbH
Lindauer Str. 21
Tettnang D-88069
DE