I read this thread yesterday. I use a download manager(GetRight), and it has a function to see if a file has been updated. So I downloaded the "new" version. Using Hash from Robin Keir gives the following result. Note that I had renamed the September update.
Both were downloaded from
http://download665.avast.com/iavs4pro/setupeng.exeFile: D:\Downloads\John\setupeng.exe
Size: 39658008 bytes
File Version: 4.8.1356.0
Modified: Tuesday, November 03, 2009, 9:44:53 PM
MD5: AFB62BD0F5D08EA2624E83C8B6056B4E
SHA1: FE5FB4F06F6521DB66EECBEB2A3B215D21D0EC09
CRC32: 736BE152
File: D:\Downloads\John\Security CD\AntiVirus\Avast_4.8.1356_Setup.exe
Size: 38786848 bytes
File Version: 4.8.1356.0
Modified: Friday, September 25, 2009, 8:04:07 PM
MD5: EF318D59457A3FD9B1F5059F4C19025D
SHA1: 6144D198B66114A7D740262A5D798E4C52B41E41
CRC32: 1B5D2F0C
Perhaps this confused them, but if they'd checked they should have known.