Updates glitch?
I had problems with a fresh installation of Avast 5 on Monday. The program repeatedly failed to connect to the updates server. Tried briefly disabling the firewall - no joy. Downloaded the definitions package from (I think) download.com; got the same error message. I didn't have time to ponder/enquire further; this was a relative's machine, needed ASAP! I put Avira on instead.
I'm still with Avast 4.8 and updating is plain sailing.