After years of using Avast, today I updated to Avast v.5 (free) on all four of my pc’s. All went well on my other computers, but on my 64 bit Windows 7 system I am unable to automatically connect to the Avast virus definitions update server. I keep getting a message that states “cannot connect to a689sm.avast.com.” I have made sure that Avast is allowed thru my firewall. I can manually update the definitions, but why am I suddenly unable to get the automatic updates? I did a complete uninstall of Avast, including a cleaning of the registry, and did a clean install, but I am having the same problem getting this program to update virus definitions automatically. Help please.
In the Avast! UI>>settings>>updates, have you specified what type of connection you have?
In proxy settings, you can also try to check “direct connection, no proxy”
Thanks Gargamel360. That did the trick.
Good to hear, glad to help 
I had same problem worked for me 2 thx ur a star m8!