Weird, I saw a red Avast popup saying that my definitions were days out of date.
So I clicked the update, which seemed to fail but it wasn't clear or informative why...
So I tried to manually update and I too get the 404.
Using WinXP (32-bit) using Avast Home version 7.0.1474, with Definitions ver 121119-1
Clicking either "Update engine and virus definitions", or "Update program" results in:
Downloading file: servers.def.vpx
Downloading file: prod-ais.vpx
Downloading file: jrog2-653.vpx
Error: HTTP server returned error 404
Last encountered error: Other HTTP error (404), while trying 208.43.71.149:80//iavs5x/jrog2-653.vpx
Also one time I saw:
Last encountered error: Cannot connect to download767.avast.com(174.36.159.202:80).
Anyways, I've done this about 2 dozen times and the IP addresses are always different.
Looks like Avast server-side to me, but I'm patient and hope its fixed by tomorrow.