Hallo,
for present (and for future probably too) versions of Linux avast, you need the 400.vps file. You can download this particular file from
http://files.avast.com/files/latest.400.vps.
When there's some restriction, but you have a proxy that can go around them, just set up this proxy in your browser, or in your environment (for wget/Lynx/Links/Elinks: export http_proxy=http://some.proxy.somewhere:port), and download the file.
Anyway, there's a script in the libavastengine package, called avastvpsreload.sh, which accepts proxiesas well (using NetAcc=2 in /etc/avastvpsupdate.conf, proxy migh be specified there, or also in the header of the script). Note that update is just about getting a particular file from particular URL, so there are always many workaround possible (redirectors, anonymizers, anonymous proxies...).
regards
pc