I am sorry for getting into the discussion, but I have been having the same problem as you: no automatic updates since I have moved from my old pc to the new laptop running windows 8/8.1. Everything works fine on my mother's pc running windows 7 also everything is fine on my cousin's laptop(which is identical to mine, except he is running windows 7 professional). I receive the streaming updates but no definition updates. I've tried leaving it for 3 days: no updates. Manual updates work fine. Also, the first update just after Avast was installed went fine by itself and that was the last automatic update I received. I am sad because I had to move from Avast because of that. I was using Avast since version 4=((((( I hope it is going to be fixed in the version 10