I have a problem with the auto-update. I had 4.1 and it was working fine then last week my firewall (Sygate) started to come up with lots of prompts for dozens of download accesses (about 3x each for 12+ addresses) every time I connected to the internet. All failed. I had auto-update on for both virus db and program. So I downloaded 4.5 and set virus db to auto-update and program update to ask. Only one prompt from firewall now but auto-update still fails. Manual update works fine. Strange! I’m perplexed? ???
try to disable the firewall and see if the auto update is working.
Is there any error message?
You should allow to avast to download updates.Set your firewall to allow this.
Good luck! 
The old problem of update with Sygate firewall 
Maybe you can set a rule to allow all connections of avast.setup.
It’s not necessary ‘server rights’ just ‘allow access’ 8)
Maybe some Sygate user (Sasha?) could help you more…
Welcome to forums.
Everything working fine here… no problems at all. See my attachment to see what services are allowed in Sygate. Btw, I’m using Sygate Personal Edition 5.6