What's in the log? Please send us the file called <avast>\setup\setup.log, e.g. to forejt at avast dot com.
There are currently four servers worldwide used to provide the updates, so it'd be quite strange if you could not access any of them. Maybe it's just that your servers.def file is somehow damaged. The servers.def file, also located in the setup subfolder, contains the list of servers avast uses to do the iAVS updates...
Hope this helps,
Vlk