I've sent you a private message here on forum, please let me know the results via email.
Also you can try this:
1. open avast settings
2. select update (connection) and press Proxy button
3. Set No proxy (direct connection)
4. press OK to confirm
5. start update manually from avast
I didn't understand what you meant by this at first, but now i've had another look at it it makes sense.
I tried it out, and success! It appears to download!
My issue now is that I have no system tray icons for Avast!, and running regedit still kills the explorer shell.
A full scan of mbam found nothing else.