I'm not saying that. I was just asking if you're using a proxy server to access the internet, and if you haven't, by any chance, configured the proxy server details in ADNM?
If you have a proxy server specified in IE, I'd recommend setting the proxy server settings on the computer group to "Direct Connection" (as opposed to the default "Autodetect") as otherwise, Avast would try to access the local mirror via proxy which may not work.
Please post a file <avast>\setup\setup.log from machine WS-DILPIE to find out what's going on, exactly.
Thanks
Vlk