n the hosts file, the listings for Avast are all 170.0.0.1.
I think you will find that is 127.0.0.1.
I also think you will find that none of the hosts file entries actually point to the real avast.com domain - they will be to things like "download-avast.com". These are all spoof domains that SpyBot has pointed to 127.0.0.1 (localhost).
Check that you don't actually have an entry in the hosts file pointing avast.com to 127.0.01 (or anything else, for that matter)!
If you ping download724.avast.com and download649.avast.com, what IP address do they resolve to?
If you are behind a hardware NAT firewall / router (basically any home router), you can pretty safely disable your SW firewall to test the updating.
Are there any relevant entries in your firewall log files, or in Event Viewer?
I use Spybot S&D, the free Malwarebytes AntiMalware, free Superantispyware and Spyware Blaster.
Not all at the same time, I hope!!
BTW, one of my home PCs is currently running the same version of Avast as you, and I have no problems updating.
SD